Ptolemaic bronze minting technology - pressed coins

[Matt Kreuzer]

Here is another theory about Ptolemaic bronze.  Were the coins pressed?
Prior to the introduction of bronze with a central dimple, Ptolemaic bronze coins were struck.  They were struck by the same method as silver and gold coins, often sharing control marks.  The flans of this type of bronze resemble tetradrachms.  One common type is c. 17g, with Zeus / Eagle with open wing.  Dates and symbols on struck Ptolemaic bronze are sometimes shared with tetradrachms.  Some have cracks.
The new method was introduced c. 264 BC.  (Dan suggests c. 260 BC).  The flans were evidently cast.  Limestone molds for the casting of Ptolemaic bronze flans were recorded at Paphos II.  The mold was evidently created by drilling into the limestone.  One side of the resulting coin had a larger diameter, which means that the edges are not at a right angle to the surface.  The reverse design was almost always placed on the larger side of the coin.  
Striking a coin involves movement of metal.  As the coin absorbs the energy of the hammer blow(s), the metal flows into the die.  The Ptolemaic bronze of the reform method has very low relief.  Comparison to silver and gold of the same era and diameter, shows a much lower relief.  (Consider a 35mm bronze of c. 260 BC against a 35mm struck Arsinoe II dekadrachm).  
If the new bronzes were "pressed" in a version of a screw press, the net movement of metal might be lower.  The technology is plausible.  The screw press was in use for pressing olives, grapes, laundry, etc.  The tithe on farms, orchards and vinyards had just switched from priestly to royal control.  (264 BC)  So the press-workers and the technology might have been especially available.  The introduction of Arsinoe II gold and silver parallels this change during this year.
If the die were simply attached to the descending press, it would spin against the coin creating concentric circles.  While this did happen occasionally, the vast majority of Ptolemaic bronzes were struck without these circles.  Instead, the dies were "pushed" by the press downward toward the coin.  At a certain point (which we know as the 12:00 die axis) the two dies would lock, while the pushing continued.  Grease would lubricate the spinning press while the die would lock on the coin, under more and more pressure.  A great deal of rotational motion energy would be translated and applied to evenly pressing the coin.  A modest hole at the center of both dies allowed a spinning pin to enter the coin during pressing.  This pin allowed retraction of the press, and easy removal of the occasional stuck bronze.
Error coins provide a glimpse into the technology used.  The large bronze shown by Dan is a very nice example of an error in this process.  Please look at the image he provided.  Initially, the dies did not slide against the press (not enough grease?) leaving the die spinning against the coin for most of one revolution.  The highest points on the die, wing feather fields, scraped against the coin creating concentric arcs of circle, until they finally locked and squeeze on the coin.  The press only squeezed for a short period of time, effacing some of the marks, and leaving a "shallow strike."  To the right of the eagle's open wing, the scraping of this high point on the die does not show.  The coin was spinning against the die for part of one revolution, with the worst scraping right before the lock, with nothing afterward.  Nothing afterward.
The overall height of the relief of this large coin is probably modest.  The concentric partial circle gives a clue to what the tightness of the threading must have been.  Tight threading would have been difficult to achieve without modern equipment, but use of a differential screw would have created the same effect.  
The type of error coins generated by the new technology included various spinning errors, spiral double-pressings, slipped pins, and multiple pin marks.  The errors common to hammer striking are scarce:  brockages, flan cracks.  Flan cracks are outright common the largest Berenike II silver produced by the alternative striking technology used at the same time.
The screw press was used for coinage in Europe in the mid-1500's.  The 1562 Elizabeth I of England silver are attractive examples.  Initially, the quality of the strike was very attractive, but the speed of striking was slower than hammered coining.  The two technologies competed on English coinage for over 100 years.  For the Ptolemaic bronze coinage, pressing probably meant more attractive, evenly struck coins.  The Ptolemaic bronze-pressing technology, as shown by dimple, was dropped between 145 and 90 BC.  Striking bronze was probably faster, but the results were less attractive.  Bronzes struck for later Ptolemies were struck on typical Ptolemaic-style bronze flans, but not with the technology which included the dimple at the center.
The dimples (and technology) occur on a number of later ancient coins from the East, including Syria, Ionia and the Balkans into Severan times.

[curtislclay]

A modest hole at the center of both dies allowed a spinning pin to enter the coin during pressing.  This pin allowed retraction of the press, and easy removal of the occasional stuck bronze.

Matt,

Doesn't your proposal require that the two indentations in the struck coin, since tied to actual holes in the two dies, should always occur in exactly the same position relative to the struck details of the types?

That is however NOT the case. On two coins struck from the same pair of dies, the indentations are usually in quite different locations relative to the types.

That seems to prove that the indentations were NOT caused by central barbs on the actual dies, as is sometimes proposed, nor by pins inserted through holes in the dies, as you are suggesting.

[Matt Kreuzer]

Curtis,

Yes, I agree that this idea requires die-links between bronzes struck with the same dies.  The small hole in the die does have a barb.  This barb becomes effectively part of the die, and should be expected to be in nearly the same place on each side. 

Examination of several Ptolemaic bronzes struck with the same die would be very helpful.  Die matches would support this idea.  The small hole may have been filled and re-drilled as part of the regular maintenance of the die.   However, overall lack of die matches does work against or eliminate this idea. 

Can you suggest Ptolemaic bronzes from same dies?

The strength of this theory is that it is a one-step process.  The other theories require two steps.  The Balkan bronzes of the Severan era show a central mark, don't show spinning, and otherwise show the high relief of a struck bronze.  Pointed tong-handling might explain those bronzes better than this idea.

Matt






Matt,

Doesn't your proposal require that the two indentations in the struck coin, since tied to actual holes in the two dies, should always occur in exactly the same position relative to the struck details of the types?

That is however NOT the case. On two coins struck from the same pair of dies, the indentations are usually in quite different locations relative to the types.

That seems to prove that the indentations were NOT caused by central barbs on the actual dies, as is sometimes proposed, nor by pins inserted through holes in the dies, as you are suggesting.

[curtislclay]

Matt,

I am referring to Roman provincial coins, where specimens from the same die pair, but with indentations in varying locations relative to the types, are abundantly common.

Never having collected or studied Ptolemaic bronze coins, I cannot say whether they too have been observed to show the same variation in dimple location on coins struck from the same dies.

[Matt Kreuzer]

Curtis,

The Balkan bronzes of the Severan era were some of the first coins I collected.   What a fun series, with so many affordable coins.

Here is an example which supports what you say. 

http://www.acsearch.info/record.html?id=72420

It is a struck incuse of Macrinus and Diadumenian from Moesia Inferior.  Note the dimple is incuse on the brockage side.  To me, this is clear evidence that the mark was there before striking.  This coin shows other signs of not being pressed:  1) a flan crack; 2) enough relief that the coin must have been struck, and 3) the brockage itself, where another coin was stuck in the die.  There is a slight raised mark before the mouth of Diadumenian where the central dimple of the other coin acted as a die to create a pimple, an incuse of the dimple. 

Certainly the blanks for this type of bronze were prepared by a method which left this mark.  A pressing machine with pinned flat dies would leave such a mark before striking (as would other forms of lathing).   Next, the coin was struck with dies.  Ptolemaic central dimples are generally more clear.  I suggest this is because the dimple was not struck over on Ptolemaic bronze.

A brockages on a dimple-type Ptolemaic bronze would be extremely interesting.  I have had a couple of later struck Ptolemaic bronze brockages, but never seen one of the dimple-type. 

Matt

[PtolemAE]

A modest hole at the center of both dies allowed a spinning pin to enter the coin during pressing.  This pin allowed retraction of the press, and easy removal of the occasional stuck bronze.

Matt,

Doesn't your proposal require that the two indentations in the struck coin, since tied to actual holes in the two dies, should always occur in exactly the same position relative to the struck details of the types?

That is however NOT the case. On two coins struck from the same pair of dies, the indentations are usually in quite different locations relative to the types.

That seems to prove that the indentations were NOT caused by central barbs on the actual dies, as is sometimes proposed, nor by pins inserted through holes in the dies, as you are suggesting.

The mis-alignment of dimples on two coin sides (frequently observed) and multiple dimples on only one side with a single dimple on the other (sometimes) are indications that 'rotating dies' are not a satisfactory explanation.  There are a couple others:

1. in the case of the illustrated coin it is mighty curious that the actual impression is a sharp single image yet the alternate theory explains this away saying that the dies rotated a perfect 360 degrees yielding nearly equally impressed circular ridges around the coin.  The gouges aren't seen as prominently in the low spots of the coin (i.e. between the eagle feathers) where we would expect to see them if consistent with the alternate explanation of how the lines arose.  The 'high spots' on the coin said to cause the gouges in the alternative theory of rotating dies are actually the low spots on the die.  The gouges are deepest were the coin relief is highest (the lowest spots of the die).  This is exactly the opposite of what was suggested in the explanation of this coin.

2. the almost perfectly uniform 12h die axes that are so typical of Ptolemaic bronzes, both before and after the introduction of the technology that resulted in dimples is hard to reconcile with rotating dies.  there's no trace of 'smudging' as the design rotated, just the gouges.  that is not to say a screw press with fixed dies would be impossible but only that rotating dies don't agree with what we see.  

3. numerous examples of what appears to be a double-strike that is sharp and somewhat horizontally displaced (not the rotational blur one might expect with rotating dies)

4. As Dave Welsh demonstrated in his presentation we can see that the gouges sometimes left behind are spiral, not circular, which presents yet another serious problem to the alternative theory.

More illustrations are apropos:

A. the obverse of the coin shown earlier.  Note it also has circular gouges yet it also has a sharp single image and a 12h die axis.  The gouges on the obverse don't seem to be aligned with any particular feature of the portrait except that they are most visible where the portrait is in highest relief, consistent with their presence *prior* the strike.  It seems that a 12h alignment with an 'error' caused by this amount of (proposed) coin slippage would be pretty exceptional with a 'slippage' of precisely 360 degrees on both sides.  We also see the circles and dimple are not aligned with those on the other side yet both design images are well-centered.  We also see the 'ridge' of raised material left on some of these gouged coins.  All the observations of this coin are easy to understand in light of a lathing process but there a 'lot of 'splainin' to do' to get them to fit the alternate theory.

B. a different coin from the same time period with a clearly off-center double-strike.  analysis of this coin's die orientations on both sides reveal that both strikes are at 12h with respect to themselves.  There are no circular lines.  It is hard to see how this coin could have been produced by rotating dies.  This coin is a 'textbook' demonstration of fixed dies struck in an ordinary fashion.

The elegant explanation provided by Dave Welsh seems to answer the question quite neatly, consistent with all the observations.  On the other hand, we must jump through a series of narrow hoops to force the evidence to fit the alternate theory.  

A two-step striking process (cast-flan lathing followed by striking) is no more troubling than the fact that these coins aren't just cast from molds altogether.  

PtolemAE

[Matt Kreuzer]

I am glad that Ptolemaic bronze errors are being considered to understand the method of production.  There are many such errors, and an accounting of these errors suggests pressing, rather than striking.

0) Misaligned dimples are a comment of Curtis about Roman Provincial coinage, which are struck.  The dimples of such coins are more subtle than those on Ptolemaic bronze coinage because they were struck, after the dimple was formed.

1) The coin in Dan's question did rotate a full 360 degrees against the die, probably further.  The effect is that of a lathe.  In the pressed theory, a break in the screw threading, or the lock meant that the coin did not receive a strike.  Instead it received the effect of a lathe.
1b) Multiple or misaligned pins are possible.
2) The early dies (pre 265 BC) were probably hinged for striking.  And the later ones locking for pressing.  If they didn't lock, every coin would simply be lathed, a series of concentric circles.
3) Slippage of one die or another isn't ruled out.  Double pressed is just like double struck, once the dies are locked in place.  However, the slippage that occurs is often rotated around the central pin, resulting in a spiral strike.  
4) Occasional spiral pattern might be explained by an foreign object, such as a grain of sand.

Here is another Ptolemaic bronze.  The pin on the reverse was set a bit too deep, or off angle.  A central pin mark slipped out.  Note the lack of roundness and where the pin slipped.  The coin spun a bit, digging the pin into the die in a circle.  This error is sharp, and not overstruck.

[LINK REMOVED BY ADMIN]

Lathing before striking is the more complicated explanation.  The lathe theory fails to:

1) explain the switch to low relief, a switch from high relief.  Why change?
2) explain any of the fairly common rotational striking errors;
3) explain the lack of flan cracks;
4) explain the lack of brockages;
5) explain pin errors such as this one; CNG 239, Lot: 245.
6) the relative clarity of central mark is not explained by the lathe theory; because striking eliminates some of the sharpness.
7) the need to lathe the surfaces of bronze is not clear.  As an occasional accident, lathing makes sense.  Use of a lathe to smooth the surface seems awkward, and no net improvement over prior coinage.
the surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.

The dimples are a portion of an overall change, associated with the 264 BC takeover of orchards, farms and vinyards.  The flan formation is changed.  The relief is lowered.  And the need for lathing is low.

Matt

[PtolemAE]

I am glad that Ptolemaic bronze errors are being considered to understand the method of production.  There are many such errors, and an accounting of these errors suggests pressing, rather than striking.

0) Misaligned dimples are a comment of Curtis about Roman Provincial coinage, which are struck.  The dimples of such coins are more subtle than those on Ptolemaic bronze coinage because they were struck, after the dimple was formed.

1) The coin in Dan's question did rotate a full 360 degrees against the die, probably further.  The effect is that of a lathe.  In the pressed theory, a break in the screw threading, or the lock meant that the coin did not receive a strike.  Instead it received the effect of a lathe.
1b) Multiple or misaligned pins are possible.
2) The early dies (pre 265 BC) were probably hinged for striking.  And the later ones locking for pressing.  If they didn't lock, every coin would simply be lathed, a series of concentric circles.
3) Slippage of one die or another isn't ruled out.  Double pressed is just like double struck, once the dies are locked in place.  However, the slippage that occurs is often rotated around the central pin, resulting in a spiral strike.  
4) Occasional spiral pattern might be explained by an foreign object, such as a grain of sand.

Here is another Ptolemaic bronze.  The pin on the reverse was set a bit too deep, or off angle.  A central pin mark slipped out.  Note the lack of roundness and where the pin slipped.  The coin spun a bit, digging the pin into the die in a circle.  This error is sharp, and not overstruck.

[LINK REMOVED BY ADMIN]

Lathing before striking is the more complicated explanation.  The lathe theory fails to:

1) explain the switch to low relief, a switch from high relief.  Why change?
2) explain any of the fairly common rotational striking errors;
3) explain the lack of flan cracks;
4) explain the lack of brockages;
5) explain pin errors such as this one; CNG 239, Lot: 245.
6) the relative clarity of central mark is not explained by the lathe theory; because striking eliminates some of the sharpness.
7) the need to lathe the surfaces of bronze is not clear.  As an occasional accident, lathing makes sense.  Use of a lathe to smooth the surface seems awkward, and no net improvement over prior coinage.
the surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.

The dimples are a portion of an overall change, associated with the 264 BC takeover of orchards, farms and vinyards.  The flan formation is changed.  The relief is lowered.  And the need for lathing is low.

Matt

Nothing about the coins we actually see that is unexplained by the lathe theory.

1. assumes facts not in evidence  
2. spirally scored coin surfaces shown on Dave Welsh's site are inconsistent with the alternative theory.
3. not only irrelevant (assumes facts not in evidence) but also clearly false.  see previously illustrated double-struck coin and one accompanying this post (with 4 cracks which should be enough).
4. assumes facts not in evidence
5. the CNG example is consistent with a fixed pin/lathe-rotated coin
6. clarity of dimples is also consistent with the lathe theory.
7. the 'why' is irrelevant to which theory works and which doesn't.  striking is more complicated than just casting.  lathing is more complicated than striking un-lathed flans.  a screw press with rotating dies is even more complicated.  
8. assumes facts not in evidence

PtolemAE

[Matt Kreuzer]

Let's add more to these arguments.

1) In c. 264 BC, Ptolemaic bronze switch from regular hammered coins, such as laureate Zeus head right / Eagle with open wing, to a different type with Zeus-Ammon head right. / One or two eagles standing.   The relief of the new coinage is lower than previous struck coinage.  Dan says, "assumes facts not in evidence" but the overall relief of the new generation of bronze coins is much lower.  Why?

2) Spirally damaged coins are not inconsistent, because the dies sometimes act as a clumsy lathe.  This was not useful or deliberate.  It was an error.
2b) Spirally struck coins are also errors.  They are nearly impossible to explain with simple dies, and fairly common.  Svor 974 and similar coins often have a bit of spiral struck reverse.
Spiral or concentric grooves are often visible on the bottoms of screw presses, as noted by K.A. Kahlil, Two Large Wine Presses at Khirbet Yajuz, Jordan.

3) Lack of flan cracks is not a complete and utter lack of anything which kind of looks like a bit of a crack.  Your coin does have tiny flan cracks at the edge consistent with the final portion of pressing of coin, not a struck coin.  Compare Ptolemaic bronze with a series of coins with the same size and diameter.  They have fewer flan cracks.  The flan cracks on large struck coins are a symptom of striking.  Ptolemaic bronze coins rarely show much in the way of cracks.  Ptolemaic silver of the same era does show cracks.  Struck Alexandria bronze diobols, hemidrachms and drachms of the Roman rulers show many deep cracks. 

4)  Lack of brockages.  Dan, I don't know what facts are "facts assumed, not in evidence."  Struck coins of this size sometimes include brockages.  Pressed brockages should be quite rare.  Show me a Ptolemaic bronze brockage with dimples?

5 and 6)  What is a problem for the central pin errors, is how clear the pin damage is.  An overstruck coin should efface a portion of the "lathe mark" but the central dimple is always quite clear.  Those Severan bronzes from Moesia Inferior are produced by a technique which must include two steps, with the first step producing the dimple.  The dimple is often clear, but not always sharp and squared at a clear right angle like it is for the Ptolemaic coins.  Striking would be expected to obscure the sharpness of the dimple.  Show me an (unworn) Ptolemaic bronze of this era without a sharp dimple?  Or a lathed blank flan?

7) Why lathe a coin?  Flattening makes sense.  And the Severan bronzes from Moesia Inferior are nice flat flans.  But flattening isn't best achieved by a lathe.  And Severan coins don't show the damage pattern caused by spinning. 

Lathing is a very awkward way to flatten metal.  On Ptolemaic error coins, lathing accidents coincide with striking accidents.  Virtually no coins are known to be lathed.  An occasional large cent (post striking) might be lathed by a machine operator to test a machine.  But pursuit of an inefficient technology for generations isn't likely to have been considered cost-efficient.

A screw press is a known technology used for this purpose, with a lengthy introduction period which competed with hammering technology for generations.  Spink’s Coins of England notes Eloye Mestrelle introduced the screw press to England in 1561, and Nicholas Briot practiced with it 1631-1632, but hammered issues were still regularly struck until early 1663, when the screw presses received the addition of peripheral machinery of Pierre Blondeau.

  The surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.  Toward the end of this type of issue, many were carelessly produced.  They often show errors.  The quality of the surfaces is far from regular.  Some of the late Ptolemaic bronze of Kyrene are little more than a dimple with a design around it.  This one has such a deep obverse dimple that the sharp rim of the dimple casts a shadow!  It must have been made during or after striking, and not heavily circulated.

http://www.acsearch.info/record.html?id=222331

And I will add 9) A screw press is not unexpected technology for this era. 




Lathing before striking is the more complicated explanation.  The lathe theory fails to:

1) explain the switch to low relief, a switch from high relief.  Why change?
2) explain any of the fairly common rotational striking errors;
3) explain the lack of flan cracks;
4) explain the lack of brockages;
5) explain pin errors such as this one; CNG 239, Lot: 245.
6) the relative clarity of central mark is not explained by the lathe theory; because striking eliminates some of the sharpness.
7) the need to lathe the surfaces of bronze is not clear.  As an occasional accident, lathing makes sense.  Use of a lathe to smooth the surface seems awkward, and no net improvement over prior coinage.
  the surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.

The dimples are a portion of an overall change, associated with the 264 BC takeover of orchards, farms and vinyards.  The flan formation is changed.  The relief is lowered.  And the need for lathing is low.

Matt



Nothing about the coins we actually see that is unexplained by the lathe theory.

1. assumes facts not in evidence 
2. spirally scored coin surfaces shown on Dave Welsh's site are inconsistent with the alternative theory.
3. not only irrelevant (assumes facts not in evidence) but also clearly false.  see previously illustrated double-struck coin and one accompanying this post (with 4 cracks which should be enough).
4. assumes facts not in evidence
5. the CNG example is consistent with a fixed pin/lathe-rotated coin
6. clarity of dimples is also consistent with the lathe theory.
7. the 'why' is irrelevant to which theory works and which doesn't.  striking is more complicated than just casting.  lathing is more complicated than striking un-lathed flans.  a screw press with rotating dies is even more complicated. 
8. assumes facts not in evidence

[PtolemAE]

Let's add more to these arguments.

1) In c. 264 BC, Ptolemaic bronze switch from regular hammered coins, such as laureate Zeus head right / Eagle with open wing, to a different type with Zeus-Ammon head right. / One or two eagles standing.   The relief of the new coinage is lower than previous struck coinage.  Dan says, "assumes facts not in evidence" but the overall relief of the new generation of bronze coins is much lower.  Why?

2) Spirally damaged coins are not inconsistent, because the dies sometimes act as a clumsy lathe.  This was not useful or deliberate.  It was an error.
2b) Spirally struck coins are also errors.  They are nearly impossible to explain with simple dies, and fairly common.  Svor 974 and similar coins often have a bit of spiral struck reverse.
Spiral or concentric grooves are often visible on the bottoms of screw presses, as noted by K.A. Kahlil, Two Large Wine Presses at Khirbet Yajuz, Jordan.

3) Lack of flan cracks is not a complete and utter lack of anything which kind of looks like a bit of a crack.  Your coin does have tiny flan cracks at the edge consistent with the final portion of pressing of coin, not a struck coin.  Compare Ptolemaic bronze with a series of coins with the same size and diameter.  They have fewer flan cracks.  The flan cracks on large struck coins are a symptom of striking.  Ptolemaic bronze coins rarely show much in the way of cracks.  Ptolemaic silver of the same era does show cracks.  Struck Alexandria bronze diobols, hemidrachms and drachms of the Roman rulers show many deep cracks. 

4)  Lack of brockages.  Dan, I don't know what facts are "facts assumed, not in evidence."  Struck coins of this size sometimes include brockages.  Pressed brockages should be quite rare.  Show me a Ptolemaic bronze brockage with dimples?

5 and 6)  What is a problem for the central pin errors, is how clear the pin damage is.  An overstruck coin should efface a portion of the "lathe mark" but the central dimple is always quite clear.  Those Severan bronzes from Moesia Inferior are produced by a technique which must include two steps, with the first step producing the dimple.  The dimple is often clear, but not always sharp and squared at a clear right angle like it is for the Ptolemaic coins.  Striking would be expected to obscure the sharpness of the dimple.  Show me an (unworn) Ptolemaic bronze of this era without a sharp dimple?  Or a lathed blank flan?

7) Why lathe a coin?  Flattening makes sense.  And the Severan bronzes from Moesia Inferior are nice flat flans.  But flattening isn't best achieved by a lathe.  And Severan coins don't show the damage pattern caused by spinning. 

Lathing is a very awkward way to flatten metal.  On Ptolemaic error coins, lathing accidents coincide with striking accidents.  Virtually no coins are known to be lathed.  An occasional large cent (post striking) might be lathed by a machine operator to test a machine.  But pursuit of an inefficient technology for generations isn't likely to have been considered cost-efficient.

A screw press is a known technology used for this purpose, with a lengthy introduction period which competed with hammering technology for generations.  Spink’s Coins of England notes Eloye Mestrelle introduced the screw press to England in 1561, and Nicholas Briot practiced with it 1631-1632, but hammered issues were still regularly struck until early 1663, when the screw presses received the addition of peripheral machinery of Pierre Blondeau.

  The surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.  Toward the end of this type of issue, many were carelessly produced.  They often show errors.  The quality of the surfaces is far from regular.  Some of the late Ptolemaic bronze of Kyrene are little more than a dimple with a design around it.  This one has such a deep obverse dimple that the sharp rim of the dimple casts a shadow!  It must have been made during or after striking, and not heavily circulated.

http://www.acsearch.info/record.html?id=222331

And I will add 9) A screw press is not unexpected technology for this era. 

Probably best to stick to the subject and not go off on unrelated tangents.

1. "the overall relief of the new generation of bronze coins is much lower."

-> assumes facts not in evidence.  i.e. just saying it doesn't make it true.

2. the issue is spiral gouges on coins which is fully consistent with the lathing and not with a rotating die without special 'excuses' like grains of sand that move spirally by magic.

3.  two dimpled Ptolemaic bronze coins with clear cracks are already illustrated.  others are available. 

-> repeating a falsehood won't make it true.

4. = why isn't there a Santa Claus?

-> assumes facts not in evidence  i.e. just saying one method will produce brockages and another wont doesn't make it true.

5. 6.  this has already been explained and fully consistent with the lathing technology. 

-> asked and answered

7. Q. why lathing?  A. lathing smooths the striking surface of cast flans, as mentioned earlier a number of times.

-> asked and answered

it's best to avoid introducing even more red herrings and irrelevant tangents into this (e.g. english coinage methods in 1561).

all the coins are dimpled Ptolemaic bronze coins *are* lathed - that's the whole point.  Dave Welsh's demonstration clearly shows how this was done and it is fully consistent with what we see on real coins.

8. the smooth die-struck surfaces of this tiny coin are consistent with lathing.

9. hypothetical theories are weighed against evidence, not what is 'expected'.  heck, Aristotle 'expected' that heavy objects fall faster than light ones - which makes perfect sense but isn't true.  Aristotle's theory also failed because it didn't fit actual evidence.

The alternative theory of rotating dies assumes unproven 'facts', relies on at least one known falsehood, and rests an 'armchair' arguments and various red-herring issues instead of explaining actual evidence.  It's a theory with real problems that won't go away while we have a perfectly good theory of lathing that meets the test of explaining real evidence.  It's a no-brainer.

PtolemAE

[Matt Kreuzer]

I'll add one more:

10) I believe that you have suggested elsewhere that Ptolemaic bronze dies lasted a long time, much longer than others.  (Was that you?)  A die used for pressing would be expected to last much longer than a die used for striking.  The stress is considerably less.  The overall lower relief (mentioned in point 1) might have allowed additional die life.

[PtolemAE]

I'll add one more:

10) I believe that you have suggested elsewhere that Ptolemaic bronze dies lasted a long time, much longer than others.  (Was that you?)  A die used for pressing would be expected to last much longer than a die used for striking.  The stress is considerably less.  The overall lower relief (mentioned in point 1) might have allowed additional die life.

A tangent citing yet another tangent (relief) that is neither proven nor demonstrably relevant to distinguishing between the two theories.  When the theory fails by the actual evidence, festooning it with tangents won't help.

assumes facts not in evidence.

PtolemAE

[Matt Kreuzer]

Does anyone beside PtolemyAE have any thoughts on this?  Thanks.

Matt


1) In c. 264 BC, Ptolemaic bronze switch from regular hammered coins, such as laureate Zeus head right / Eagle with open wing, to a different type with Zeus-Ammon head right. / One or two eagles standing.   The relief of the new coinage is lower than previous struck coinage.  Dan says, "assumes facts not in evidence" but the overall relief of the new generation of bronze coins is much lower.  Why?

2) Spirally damaged coins are not inconsistent, because the dies sometimes act as a clumsy lathe.  This was not useful or deliberate.  It was an error.
2b) Spirally struck coins are also errors.  They are nearly impossible to explain with simple dies, and fairly common.  Svor 974 and similar coins often have a bit of spiral struck reverse.
Spiral or concentric grooves are often visible on the bottoms of screw presses, as noted by K.A. Kahlil, Two Large Wine Presses at Khirbet Yajuz, Jordan.

3) Lack of flan cracks is not a complete and utter lack of anything which kind of looks like a bit of a crack.  Your coin does have tiny flan cracks at the edge consistent with the final portion of pressing of coin, not a struck coin.  Compare Ptolemaic bronze with a series of coins with the same size and diameter.  They have fewer flan cracks.  The flan cracks on large struck coins are a symptom of striking.  Ptolemaic bronze coins rarely show much in the way of cracks.  Ptolemaic silver of the same era does show cracks.  Struck Alexandria bronze diobols, hemidrachms and drachms of the Roman rulers show many deep cracks.  

4)  Lack of brockages.  I don't know what facts are "facts assumed, not in evidence."  Struck coins of this size sometimes include brockages.  Pressed brockages should be quite rare.  Show me a Ptolemaic bronze brockage with dimples?

5 and 6)  What is a problem for the central pin errors, is how clear the pin damage is.  An overstruck coin should efface a portion of the "lathe mark" but the central dimple is always quite clear.  Those Severan bronzes from Moesia Inferior are produced by a technique which must include two steps, with the first step producing the dimple.  The dimple is often clear, but not always sharp and squared at a clear right angle like it is for the Ptolemaic coins.  Striking would be expected to obscure the sharpness of the dimple.  Show me an (unworn) Ptolemaic bronze of this era without a sharp dimple?  Or a lathed blank flan?

7) Why lathe a coin?  Flattening makes sense.  And the Severan bronzes from Moesia Inferior are nice flat flans.  But flattening isn't best achieved by a lathe.  And Severan coins don't show the damage pattern caused by spinning.  

Lathing is a very awkward way to flatten metal.  On Ptolemaic error coins, lathing accidents coincide with striking accidents.  Virtually no coins are known to be lathed.  An occasional large cent (post striking) might be lathed by a machine operator to test a machine.  But pursuit of an inefficient technology for generations isn't likely to have been considered cost-efficient.

A screw press is a known technology used for this purpose, with a lengthy introduction period which competed with hammering technology for generations.  Spink’s Coins of England notes Eloye Mestrelle introduced the screw press to England in 1561, and Nicholas Briot practiced with it 1631-1632, but hammered issues were still regularly struck until early 1663, when the screw presses received the addition of peripheral machinery of Pierre Blondeau.

  The surfaces of Ptolemaic bronzes (from this time period) are often not always flat, and are alway have a dimple.  Toward the end of this type of issue, many were carelessly produced.  They often show errors.  The quality of the surfaces is far from regular.  Some of the late Ptolemaic bronze of Kyrene are little more than a dimple with a design around it.  This one has such a deep obverse dimple that the sharp rim of the dimple casts a shadow!  It must have been made during or after striking, and not heavily circulated.

http://www.acsearch.info/record.html?id=222331

9) A screw press is not unexpected technology for this era.

10) I believe that you have suggested elsewhere that Ptolemaic bronze dies lasted a long time, much longer than others.  (Was that you?)  A die used for pressing would be expected to last much longer than a die used for striking.  The stress is considerably less.  The overall lower relief (mentioned in point 1) might have allowed additional die life.

[Dino]

I don't buy the spinning die theory. 

1.  There are enough errors on ancient coins and certainly enough examples of ptolemaic coins that we should see evidence of "smudged" coins where the rotation smudges the image.  I am not aware of any such examples.

2.  If the die spun or turned in sucha fashion would either the right or left sides of the images in the die (depending on the direction of the spin) wear more as metal scrapes across the edge than the other side?  Wouldn't we see signs of that wear in some coins?  Can you show me some examples like that?

Also, why try to come up with such a complicated explanation/system?  Let's consider the principle of lex parsimoniae or Occam's razor, which states that the simplest explanation is most likely true.

To me the simplest explanation is that a lathe was used in making the flan.  The coin was struck.  That theory explains everything that has been shown on these coins.  The more complex rotating die theory does not.

[Matt Kreuzer]

Great questions Dino.

In this theory, the die shouldn't be spinning.  Just the screw behind it, and the pin which is at its center.  The grease behind the die keeps the spinning screw from spinning the die.  Only in unusual cases (less than 1%) does the die act like a lathe, producing an error coin.  Such coins are likely to be poorly struck, as the dies latch with each other only near the end of the pressing.  The energy intended for striking creates lathe marks instead.  Given the hard-stop of the locking mechanism, I wouldn't expect smooshy pressings.

1.  The first coin posted in this thread shows some of this.  To the left of the eagle's open wing, we can see a series of concentric circles, where slightly high points on the fairly flat die left marks.  The die finally latched to a hard stop and squeezed.  To the right of the eagle's open wing, we see no marks.  Nothing.

The various spiral struck coins are examples of this too.  

2.  Die wear?  The dies weren't meant to be lathes.  They could have been spun both ways.  I can't show you die wear.  Similarly, Roman denarii die occasionally made brockages.  But you can't show brockage-wear because the dies weren't made to make brockages.  Concentrically marked coins are error coins, with accidental lathing.

Is this complicated?  I think it's a reasonable way to craft coins.  I'd like to build a press like this to see how error might form.

The central mark was created during or after the striking.  Otherwise, why would this coin have such a high rim around the central mark?  

http://www.acsearch.info/record.html?id=222331

Lathing before striking means that the strike would flatten the sharp rim of this coin.  Why is the high rim of the central mark not flattened?

Lack of striking cracks in Ptolemaic bronze during this period is a key factor that supports pressing over striking.  Two images were posted by Dan to dispute the assertion that Ptolemaic bronzes lack cracks.  1) The Isis coin has tiny rim cracks that support pressing.  The pressed c. 1970 Rosa copies occasionally show such edge cracks, as do other pressed coins.  2) The second image shows a freakishly-rare, double pressed image, with a tiny crack where the second off-center image met the first.  Well, that is a crack.  But it is not a regular striking crack.  (As I look at the laureate Zeus and lack of a central dimple, I realize that this is an earlier pre-265 BC struck issue anyway).  Striking cracks are common in the non-dimpled, struck bronzes which precede and follow this series.  I have handled large groups of Roman Egyptian drachms, and perhaps 15% have deep, open flan splits similar to the one depicted.  However, they are not secondary off-center struck.  The striking of a bronze coin often leads to cracks.  Pressing leaves far fewer cracks.

Matt

I don't buy the spinning die theory.  

1.  There are enough errors on ancient coins and certainly enough examples of ptolemaic coins that we should see evidence of "smudged" coins where the rotation smudges the image.  I am not aware of any such examples.

2.  If the die spun or turned in sucha fashion would either the right or left sides of the images in the die (depending on the direction of the spin) wear more as metal scrapes across the edge than the other side?  Wouldn't we see signs of that wear in some coins?  Can you show me some examples like that?

Also, why try to come up with such a complicated explanation/system?  Let's consider the principle of lex parsimoniae or Occam's razor, which states that the simplest explanation is most likely true.

To me the simplest explanation is that a lathe was used in making the flan.  The coin was struck.  That theory explains everything that has been shown on these coins.  The more complex rotating die theory does not.

[PtolemAE]

Great questions Dino.

In this theory, the die shouldn't be spinning.  Just the screw behind it, and the pin which is at its center.  The grease behind the die keeps the spinning screw from spinning the die.  Only in unusual cases (less than 1%) does the die act like a lathe, producing an error coin.  Such coins are likely to be poorly struck, as the dies latch with each other only near the end of the pressing.  The energy intended for striking creates lathe marks instead.  Given the hard-stop of the locking mechanism, I wouldn't expect smooshy pressings.

1.  The first coin posted in this thread shows some of this.  To the left of the eagle's open wing, we can see a series of concentric circles, where slightly high points on the fairly flat die left marks.  The die finally latched to a hard stop and squeezed.  To the right of the eagle's open wing, we see no marks.  Nothing.

The various spiral struck coins are examples of this too.  

2.  Die wear?  The dies weren't meant to be lathes.  They could have been spun both ways.  I can't show you die wear.  Similarly, Roman denarii die occasionally made brockages.  But you can't show brockage-wear because the dies weren't made to make brockages.  Concentrically marked coins are error coins, with accidental lathing.

Is this complicated?  I think it's a reasonable way to craft coins.  I'd like to build a press like this to see how error might form.

The central mark was created during or after the striking.  Otherwise, why would this coin have such a high rim around the central mark?  

http://www.acsearch.info/record.html?id=222331

Lathing before striking means that the strike would flatten the sharp rim of this coin.  Why is the high rim of the central mark not flattened?

Lack of striking cracks in Ptolemaic bronze during this period is a key factor that supports pressing over striking.  Two images were posted by Dan to dispute the assertion that Ptolemaic bronzes lack cracks.  1) The Isis coin has tiny rim cracks that support pressing.  The pressed c. 1970 Rosa copies occasionally show such edge cracks, as do other pressed coins.  2) The second image shows a freakishly-rare, double pressed image, with a tiny crack where the second off-center image met the first.  Well, that is a crack.  But it is not a regular striking crack.  (As I look at the laureate Zeus and lack of a central dimple, I realize that this is an earlier pre-265 BC struck issue anyway).  Striking cracks are common in the non-dimpled, struck bronzes which precede and follow this series.  I have handled large groups of Roman Egyptian drachms, and perhaps 15% have deep, open flan splits similar to the one depicted.  However, they are not secondary off-center struck.  The striking of a bronze coin often leads to cracks.  Pressing leaves far fewer cracks.

1. Q. Why is the high rim of the central mark not flattened? 

A. because the dimple is at the lowest carved point of the striking die, as explained repeatedly being perfectly consistent with coins being struck after the dimples were created by a lathe process.

asked and answered.

2. "1) The Isis coin has tiny rim cracks that support pressing." 

It's difficult to respond to the critique of a requested demonstration of dimple coins with cracks, the only critique which is that they are not the kind of cracks the critic wants.  I haven't seen Rosa 'pressed' copies of 48mm Ptolemaic bronze coins (the ancient ones do have dimples).  The problem lies not with the coin showing cracks, rather with the 'spining dies' theory.

3. "a freakishly-rare, double pressed image, with a tiny crack where the second off-center image met the first.  Well, that is a crack.  But it is not a regular striking crack.  (As I look at the laureate Zeus and lack of a central dimple, I realize that this is an earlier pre-265 BC struck issue anyway)."

Actually there are very good reasons the latter is not the case.  It's weight, diameter, reverse design of a closed-wing single eagle, as well as the Zeus style (more fully elucidated in a forthcoming paper for which this coin was considered for illustration of the point) firmly put it in the 'post-reform' time period.  Other examples of the same catalog # - Svoronos 760 - of matching size, weight, design, etc., do show the dimples.  Illustrations on request.  This denomination/size/weight/type does not even exist in the pre-reform (pre ca. 260 BC) bronze coinage series. 

It is a striking crack but not because it precedes the time at which lathe-dimple technology came into use.  This is an unusual case where we do see the dimple partly effaced (upon close inspection about 1/2 of the dimple remains) - precisely because the coin was struck nearly 50% off-center.  At least part of the dimple was apparently hit by a low-carved part of the die on the first (off-center) strike.  IOW, once again completely consistent with lathing-dimple concept - a doubly useful demonstration of it.

Of course we don't know if most 'errors' (severe cracks) were simply melted down and re-cast or if badly cracked/broken coins just don't hit the commercial trade or even if the existence of cracks tells us more about alloys than minting methods.  But we do know that there are many edge-cracked coins with dimples.  Two have been illustrated and it's easy to illustrate more.  Actually the whole 'crack' issue is probably not even relevant to distinguishing whether one theory or the other bears up.  Contrary to the claim of the proponent of the 'spinning die' theory, their existence is easy to demonstrate.

3. "Striking cracks are common in the non-dimpled, struck bronzes which precede and follow this series." 

assumes facts not in evidence but probably irrelevant to the theory of how the dimples were imparted to the coin flans.


4. "In this theory, the die shouldn't be spinning.  Just the screw behind it, and the pin which is at its center."

Yet in an earlier post the theory was stated as:

"I suggest that the dimple was applied last, as the spinning die withdrew, pivoting on the central dimple-making pin."

The spinning die theory is now the non-spinning die theory.  This is getting very hard to follow.

A screw press is a potentially interesting idea, but large bronze coins are a lot harder to squash than grapes.  Even the existence of the technology is not, afaik, archaeologically verified as early as 260BC.  It could have preceded the usual historical dates associated with Archimedes' machines (e.g. the screw itself) at about that time.  In this thread its application to coinage begins in 1561, 1800 years later.  Perhaps we will see a demo model when its proponent builds one and shows how it could be used in ca. 260BC to create 48 mm bronze coins with dimples.  A screw press with spinning (or are they now non-spinning?) dies with locking mechanisms, etc. is a very complicated 16th century answer to a 3rd C. BC question that has a simpler answer.  As Dino pointed out, parsimony (Occam's razor) favors the latter. 

PtolemAE

[Matt Kreuzer]

1.  Still not answered Dan.

REPEAT:   The central mark was created during or after the striking.  Otherwise, why would this coin have such a high rim around the central mark? 

http://www.acsearch.info/record.html?id=222331

That rim should be flattened by the striking, if it happened afterward.

2.  An actual severe flan crack on a Ptolemaic bronze with dimple would be helpful for your view.

Anybody else have any thoughts?

Matt

Great questions Dino.

In this theory, the die shouldn't be spinning.  Just the screw behind it, and the pin which is at its center.  The grease behind the die keeps the spinning screw from spinning the die.  Only in unusual cases (less than 1%) does the die act like a lathe, producing an error coin.  Such coins are likely to be poorly struck, as the dies latch with each other only near the end of the pressing.  The energy intended for striking creates lathe marks instead.  Given the hard-stop of the locking mechanism, I wouldn't expect smooshy pressings.

1.  The first coin posted in this thread shows some of this.  To the left of the eagle's open wing, we can see a series of concentric circles, where slightly high points on the fairly flat die left marks.  The die finally latched to a hard stop and squeezed.  To the right of the eagle's open wing, we see no marks.  Nothing.

The various spiral struck coins are examples of this too.  

2.  Die wear?  The dies weren't meant to be lathes.  They could have been spun both ways.  I can't show you die wear.  Similarly, Roman denarii die occasionally made brockages.  But you can't show brockage-wear because the dies weren't made to make brockages.  Concentrically marked coins are error coins, with accidental lathing.

Is this complicated?  I think it's a reasonable way to craft coins.  I'd like to build a press like this to see how error might form.

The central mark was created during or after the striking.  Otherwise, why would this coin have such a high rim around the central mark?  

http://www.acsearch.info/record.html?id=222331

Lathing before striking means that the strike would flatten the sharp rim of this coin.  Why is the high rim of the central mark not flattened?

Lack of striking cracks in Ptolemaic bronze during this period is a key factor that supports pressing over striking.  Two images were posted by Dan to dispute the assertion that Ptolemaic bronzes lack cracks.  1) The Isis coin has tiny rim cracks that support pressing.  The pressed c. 1970 Rosa copies occasionally show such edge cracks, as do other pressed coins.  2) The second image shows a freakishly-rare, double pressed image, with a tiny crack where the second off-center image met the first.  Well, that is a crack.  But it is not a regular striking crack.  (As I look at the laureate Zeus and lack of a central dimple, I realize that this is an earlier pre-265 BC struck issue anyway).  Striking cracks are common in the non-dimpled, struck bronzes which precede and follow this series.  I have handled large groups of Roman Egyptian drachms, and perhaps 15% have deep, open flan splits similar to the one depicted.  However, they are not secondary off-center struck.  The striking of a bronze coin often leads to cracks.  Pressing leaves far fewer cracks.

1. Q. Why is the high rim of the central mark not flattened? 

A. because the dimple is at the lowest carved point of the striking die, as explained repeatedly being perfectly consistent with coins being struck after the dimples were created by a lathe process.

asked and answered.

2. "1) The Isis coin has tiny rim cracks that support pressing." 

It's difficult to respond to the critique of a requested demonstration of dimple coins with cracks, the only critique which is that they are not the kind of cracks the critic wants.  I haven't seen Rosa 'pressed' copies of 48mm Ptolemaic bronze coins (the ancient ones do have dimples).  The problem lies not with the coin showing cracks, rather with the 'spining dies' theory.

3. "a freakishly-rare, double pressed image, with a tiny crack where the second off-center image met the first.  Well, that is a crack.  But it is not a regular striking crack.  (As I look at the laureate Zeus and lack of a central dimple, I realize that this is an earlier pre-265 BC struck issue anyway)."

Actually there are very good reasons the latter is not the case.  It's weight, diameter, reverse design of a closed-wing single eagle, as well as the Zeus style (more fully elucidated in a forthcoming paper for which this coin was considered for illustration of the point) firmly put it in the 'post-reform' time period.  Other examples of the same catalog # - Svoronos 760 - of matching size, weight, design, etc., do show the dimples.  Illustrations on request.  This denomination/size/weight/type does not even exist in the pre-reform (pre ca. 260 BC) bronze coinage series. 

It is a striking crack but not because it precedes the time at which lathe-dimple technology came into use.  This is an unusual case where we do see the dimple partly effaced (upon close inspection about 1/2 of the dimple remains) - precisely because the coin was struck nearly 50% off-center.  At least part of the dimple was apparently hit by a low-carved part of the die on the first (off-center) strike.  IOW, once again completely consistent with lathing-dimple concept - a doubly useful demonstration of it.

Of course we don't know if most 'errors' (severe cracks) were simply melted down and re-cast or if badly cracked/broken coins just don't hit the commercial trade or even if the existence of cracks tells us more about alloys than minting methods.  But we do know that there are many edge-cracked coins with dimples.  Two have been illustrated and it's easy to illustrate more.  Actually the whole 'crack' issue is probably not even relevant to distinguishing whether one theory or the other bears up.  Contrary to the claim of the proponent of the 'spinning die' theory, their existence is easy to demonstrate.

3. "Striking cracks are common in the non-dimpled, struck bronzes which precede and follow this series." 

assumes facts not in evidence but probably irrelevant to the theory of how the dimples were imparted to the coin flans.


4. "In this theory, the die shouldn't be spinning.  Just the screw behind it, and the pin which is at its center."

Yet in an earlier post the theory was stated as:

"I suggest that the dimple was applied last, as the spinning die withdrew, pivoting on the central dimple-making pin."

The spinning die theory is now the non-spinning die theory.  This is getting very hard to follow.

A screw press is a potentially interesting idea, but large bronze coins are a lot harder to squash than grapes.  Even the existence of the technology is not, afaik, archaeologically verified as early as 260BC.  It could have preceded the usual historical dates associated with Archimedes' machines (e.g. the screw itself) at about that time.  In this thread its application to coinage begins in 1561, 1800 years later.  Perhaps we will see a demo model when its proponent builds one and shows how it could be used in ca. 260BC to create 48 mm bronze coins with dimples.  A screw press with spinning (or are they now non-spinning?) dies with locking mechanisms, etc. is a very complicated 16th century answer to a 3rd C. BC question that has a simpler answer.  As Dino pointed out, parsimony (Occam's razor) favors the latter. 

PtolemAE

[PtolemAE]

1.  Still not answered Dan.

REPEAT:   The central mark was created during or after the striking.  Otherwise, why would this coin have such a high rim around the central mark? 

http://www.acsearch.info/record.html?id=222331

That rim should be flattened by the striking, if it happened afterward.

2.  An actual severe flan crack on a Ptolemaic bronze with dimple would be helpful for your view.

Anybody else have any thoughts?

Matt

1.  Asked and answered - several times.  That's enough.

2.  Asked and answered - several times.  That's enough.

Good luck with the non-spinning spinning die theory.

PtolemAE

[Dino]

Matt-

Coins had been struck for hundreds of years at the point you suggest this innovation of dual spinning pins to remove a coin from a press was supposedly developed.

What's the evidence that there would ever be a need for the innovation? 

What's the evidence that coins repeatedly got stuck in dies to the extent that some new solution or innovation was needed to remove the coins from the dies?

Brockages right? 

A brockage is a result of a coin stuck in a die.  Fairly rare.  I don't think I've ever seen any ptolemaic brockages.

So why would there be a need for this complex system you suggest where the dies are carved, holes are carefully and accurately drilled through them so they can be mounted on a press with dual moving and spinning pins, and a press is actually designed and built that allows for the insertion of these dies and these moving pins?

[Dino]

Two more points:

1.  for your theory to work, both sides of the coin would have to be so stuck in the press that the spinning pins literally drill dimples into the coin as the pins separate the coin from the press.  Imagine the stress on the pin and the entire mechanism for that to be the case. 

2.  There would have to be a few coins where the pin wasn't needed to push the coin out of the press.  At least one side anyway.  I would imagine most of them, frankly.  In those cases, shouldn't you see coins with little pillars in the center rather than dimples where the metal from the coin was pushed into the hole in the die?  Can you show me any coins like that?

[PtolemAE]

Two more points:

1.  for your theory to work, both sides of the coin would have to be so stuck in the press that the spinning pins literally drill dimples into the coin as the pins separate the coin from the press.  Imagine the stress on the pin and the entire mechanism for that to be the case. 

2.  There would have to be a few coins where the pin wasn't needed to push the coin out of the press.  At least one side anyway.  I would imagine most of them, frankly.  In those cases, shouldn't you see coins with little pillars in the center rather than dimples where the metal from the coin was pushed into the hole in the die?  Can you show me any coins like that?

That's an interesting point.  If even the tip a (hypothetical) pin occasionally broke off or wore away it would leave a little cavity that would behave like a carved part of the die, adding relief (a little round pillar or burr) to the location on the coin where the pin used to be.  I've never seen even a hint of that.

PtolemAE

[Matt Kreuzer]

1. Certainly the pins in this theory would be under some stress.  The pin is spinning into the center of the coin just before the dies lock.  That lock must be pretty strong too.  The pins could be replaced.  Use of the strongest metal "steel" for pins would make sense.  The odd lathe used in the other theory would have similar stress on the pin. 

2. That specific coin that I have mentioned has such a metal issue. 

http://www.acsearch.info/record.html?id=222331

with obverse cross-section like this:

---------------------^v^-------------------------

The highest point of the metal on the obverse extends up, up past where it would have been flattened in a strike.  It extends so far that it casts a bit of shadow in the lighting.  There is just a little wear on the patina at the very high points.

Small bronzes from this late period are more likely to have such a high rim around the dimple.  The general appearance of the coin is that it was less well prepared than earlier, larger coins.  The overall best prepared Ptolemaic bronze coins seem to be from the reign of Ptolemy III.  Those of Ptolemy II are often of good style and production quality, while those of Ptolemy IV are not bad.  However, the craftsmanship of the same later issues are more often rather clumsy.

Two more points:

1.  for your theory to work, both sides of the coin would have to be so stuck in the press that the spinning pins literally drill dimples into the coin as the pins separate the coin from the press.  Imagine the stress on the pin and the entire mechanism for that to be the case. 

2.  There would have to be a few coins where the pin wasn't needed to push the coin out of the press.  At least one side anyway.  I would imagine most of them, frankly.  In those cases, shouldn't you see coins with little pillars in the center rather than dimples where the metal from the coin was pushed into the hole in the die?  Can you show me any coins like that?

That's an interesting point.  If even the tip a (hypothetical) pin occasionally broke off or wore away it would leave a little cavity that would behave like a carved part of the die, adding relief (a little round pillar or burr) to the location on the coin where the pin used to be.  I've never seen even a hint of that.

PtolemAE

[Matt Kreuzer]

Dino,

The purpose of the machine was to press coins evenly, not to remove a stuck coin.  The occasional lathing of a coin was an accident, not the usual desired result.  Similarly, the use of the pin to scrape out a stuck coin was only a modest reason for its use.  The purpose of the pins was to transfer the energy of the spinning mass behind the die into the coin very evenly. 

1) Why at this time?  Several reasons.

a) One possibility is that the Ptolemies bronzes had just been copied by another government!  During late World War II, the Germans counterfeited Allied money, especially British five pound notes.  The similar situation (and it's only one of several possibilities) may have been the c. 265 BC Sicilian striking of Ptolemaic c. 17g bronzes.  If these were struck by a non-Ptolemaic entity (such as Hieron II?) then they are actually unofficial.  This method of production was perhaps one more check on such counterfeits.

b) Another possibility for the change relates to the use of bronze to bring in silver.  Use of bronze allowed the Ptolemaic king to accept silver in payment for taxes, while spending bronze in his realm.  The new bronzes had the Egyptian-like Zeus-Ammon, rather than the more Greek Zeus.  They circulated deeper into Upper Egypt than previous coinage, allowing taxes to be collected more easily than previous ways.

c) Large designs on large planchets were needed, larger than bronzes had been struck.  Striking very big bronzes was difficult.  This method would have generally provided a nice even pressing, a consistent product.

d)  Low relief is a symptom of this type of production.  Striking would have allowed higher relief.  It is interesting that struck coins with high relief were produced in gold and silver during this period.

e) The technology is not beyond the period.  The screw had actually been in use long before Archimedes (287-212 BC) who probably trained in Alexandria.  One possible inventor of the screw is Archytas of Tarentum (428-347 BC).  Presses were used for olives and grapes and other produce.  Depending on the scale of the press, the energy applied could have been enormous.

f) The 264 BC changes in the taxation of orchards, farms and vineyards would have made technology of those places more available to the government.  A good craftsman (or group of them) would have been ideal to transfer this technology to a new purpose.

g) The level of mechanical science in the Ptolemaic Kingdom was high at this time.  Alexandria and the entire Ptolemaic Kingdom was a center of science and learning.  The wealth and good judgement of Ptolemy II provided an environment that fostered this.

h)  Gold and silver were also being transformed in 264 BC.  New designs were introduced.  The weight standard for gold was slightly revised.  This type fits into the overall transformation of the mints.

2) The evidence that previous coins got repeated stuck in the die?  Modest.  Brockages of earlier struck coins are known.  They may have been a chore to peel off the die.  But they are scarce to rare.  The purpose of the pin is only slightly for the purpose of reducing brockages.  Without the pin, the strong force behind the die could have slipped.  This central pin helped allow the force to be conveyed evenly to the entire coin.


Why lathe coins this way at all?  The surfaces are decent, equal to the nice surfaces of contemporary struck bronze coins.  Use of an extra step to lathe every coin in this odd way is certainly a wasteful step.  Such wasteful steps add no value in a mint.  Wasteful steps are likely to have been eliminated quickly.  Lathing might have been better accomplished through use of a larger wheel without central pin.  The purpose of the lathe seems to have been to provide marks, and to produce error coins! 

Matt

Matt-

Coins had been struck for hundreds of years at the point you suggest this innovation of dual spinning pins to remove a coin from a press was supposedly developed.

What's the evidence that there would ever be a need for the innovation? 

What's the evidence that coins repeatedly got stuck in dies to the extent that some new solution or innovation was needed to remove the coins from the dies?

Brockages right? 

A brockage is a result of a coin stuck in a die.  Fairly rare.  I don't think I've ever seen any ptolemaic brockages.

So why would there be a need for this complex system you suggest where the dies are carved, holes are carefully and accurately drilled through them so they can be mounted on a press with dual moving and spinning pins, and a press is actually designed and built that allows for the insertion of these dies and these moving pins?

[Matt Kreuzer]

Pressed cracks.

I was asked by PtolemyAE to provide examples of pressed cracks in a coin.   

Here is one from the fake section of this site.

https://www.forumancientcoins.com/fakes/displayimage.php?album=26&pos=9

Note how the multiple flan cracks extend only a bit into the edge of the flan.

By comparison, a struck coin with a flan crack often goes deep into the flan.

Here is a Byzantine bronze struck coin with a flan crack:

https://www.forumancientcoins.com/catalog/roman-and-greek-coins.asp?param=45637q00.jpg&vpar=941&zpg=54902&fld=https://www.forumancientcoins.com/Coins2/

In general, the deep single (and double) flan cracks are a type of failure in the metal under the heavy pressure of striking.

The lighter pressure of pressing produces multiple modes cracks, a different type of metal failure.

The four cracks on the nice Isis bronze are more similar to the pressed coin.

[Dino]

Matt-

I understand that you're passionate about your theory, but it seems that you're looking at exceptions in the coins to prove your point and ignoring examples that clearly disprove your point.

Case in point.  You didn't show us a coin with any burr or pillar cause by a "broken pin."  You showed us a coin with a strange dimple that can be explained by any number of reasons.

I think I have an example here that disproves your theory.  If there's a hole drilled in the center of the dies, the holes or dimples in the coins should appear in the center of the die, even if the flan is not perfectly centered.  Below is an example which shows that's just not the case.  The hole or dimple is nowhere near the center of the die image.  It is in the center of the flan, however.

Clear conclusion, hole is the result of the manufacturing of the flan, not the striking of the coin. 

By the way, the coin below is exactly the same attribution as the coin you link to in reply #22.

As to your responses to the "why now" question, they appear to be pure speculation.  And I'm honestly not sure that the speculation itself even supports your theory.

It's good to have a theory and to advocate it to test it.  At some point, however, when it's clear that the theory doesn't work, it's time to move on to something else....

By the way, check out the flan crack.