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Author Topic: Strange coin of Constantine II ??  (Read 7908 times)

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Offline Tanit

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Strange coin of Constantine II ??
« on: December 14, 2008, 06:22:05 pm »
Hi

Can you explain how this strange coin was struck  ?

Thanks

Offline Steve Minnoch

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Re: Strange coin of Constantine II ??
« Reply #1 on: December 14, 2008, 06:26:01 pm »
It's called a brockage.

The previous coin was stuck in the reverse die when this coin was struck, hence leaving this strange reverse-incuse image of the obverse, rather than a normal reverse.

Steve

Offline Steve Minnoch

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Offline Tanit

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Re: Strange coin of Constantine II ??
« Reply #3 on: December 14, 2008, 06:41:15 pm »
Thank you Steve

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #4 on: December 15, 2008, 10:21:34 am »
This coin shows something that I have yet to be explained anywhere. 
How does the incuse image become larger than the original image and yet show no distortion of the fine detail even keeping proportional distances and size?
As far as I can tell, the obverse and reverse are from the same die.  Yet, the legend is clearly on the edge of the incuse side while the beaded border is fully on the obverse.  If you struck the obverse of this coin with the same size flan, obviously the obverse would tend to flatten and become larger.  But, in doing so, certainly the higher details, the hair especially would also be flattened, spread out and may even become indistinct (try hitting this coin with a bronze hammer).  One would also expect the outside raised rim of the coin to contact the new planchet and we would see evidence of the border dots.  On this coin, and many brockages I have seen lately, the incuse is often as well struck or better than the obverse with no distortions (except for larger size) or loss of detail at all.  Can someone esplain how this happens?
Jeff Clark

virtus42

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Re: Strange coin of Constantine II ??
« Reply #5 on: December 15, 2008, 11:33:20 am »
Jeff, I don't see any reason to expect the incuse image to be indistinct on non-proportially scaled... The difference between striking a flan with (incuse) die or an (obtuse) coin is mostly just that with the die the flan is presed into and  contained by the incuse design, whereas with the coin very similar to squishing a seal ring into a blob of sealing wax, or striking a coin with a punch for a deliberate incuse impression) the force is outwards rather than inwards and the impression is therefore larger rather than smaller than the original. Evidently a fresh struck coin makes quite a servicable punch for a brockage, and it's not really surprising given that metal becomes work-hardened and so the surface of the struck coin is going to be harder than the soft/annealed and hotter fresh flan is is striking. I've also read that one type of modern forgery uses plastic dies, which although they don't last for long can also make a very sharp impression for a limited number of strikes.

Ben

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #6 on: December 15, 2008, 03:12:21 pm »
Ben,
What you have said is pretty much correct in so far as it goes.  I am not worried about proportionality of the design nor that it is a fairly good likeness of the original.  I am not even worried that the basic design should be slightly larger.  What bothers me is that the raised border of the coin should hit at relatively the same time as the letters and be well within the flan on both sides.  And, like wax under a punch, the whole design remains. How then does it disappear without a trace to be replaced only by a larger version of the obverse?  And, while expansion may occur, it must be accompanied by some slight loss of detail....ie there cant be more detail in the larger version than the original can  there? 
Jeff Clark

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #7 on: December 15, 2008, 04:39:02 pm »
The link above illustrates my point exactly.  All but the Constantine II shown are fairly consistent in size on both sides, show some of the border when it should be there and in at least one case even shows two different dies.  The Con II coin in the link, just like the one in this thread and many others I have seen lately all exhibit something a little more out of the norm....and all I would like to know is why?
Jeff Clark

Offline Steve Minnoch

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Re: Strange coin of Constantine II ??
« Reply #8 on: December 15, 2008, 04:43:36 pm »
Perhaps because of the metal?  The silver brockages illustrated don't seem as deeply imprinted as the Constantine-era bronze.

I'd expect an incuse image to be larger, if fully imprinted - if you think about it, doesn't the normal image have to fit completely inside it?

Steve

Offline curtislclay

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Re: Strange coin of Constantine II ??
« Reply #9 on: December 15, 2008, 05:00:53 pm »
Jeff,

Despite careful reading of your posts three times, I am unable to understand what you find odd and inexplicable about the Constantine II brockage. Could you try again to explain it to me?

Which brockage in the linked article do you consider to be the product of two different dies?  In a quick look all seemed to me to show the same die on both sides, as one would expect.
Curtis Clay

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #10 on: December 15, 2008, 05:27:57 pm »
Curtis,
The first coin after the diagrams with female head seems to show two different dies.  I could be wrong, but there are a number of differences it seems to me.
As for explanation of what I mean, that may be harder as I have tried 3 times now and appear to be the only one able to understand or worry about it.
The design on the incuse side is considerably larger than that on the obverse.  I expect some variation in size, but if you look at the Victory on prow coin in the link above, even in bronze, it is not normally a huge variation.  If you center a planchet, that is the same size as those in both of these Constantine II coins, over another coin of the same size and strike it, doesn't the whole design transfer?  Why are the border dots lost?  Why does the image grow so much that they are lost?  What possible mechanism creates this phenomenon without some distortion of the design?
Jeff Clark

Offline Heliodromus

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Re: Strange coin of Constantine II ??
« Reply #11 on: December 15, 2008, 05:28:35 pm »
Jeff,
I think the reason the border doesn't appear on the brockage is because it's off flan! To prove this, you need to take a few measurements. First note that the obv/rev photos are to scale - they are both the same width. Now try measuring from N-to-N across the coin (i.e from N of CON to N of NOB), measuring from inside-to-inside and outside-to-outside on both sides of the coin. What you'll notice is that not only is the N-N outside-outside measurement larger on the brockage side, but also the N-N inside-to-inside measurement is larger which means that the whole design is stretched on the brockage side, not just independent device-by-device (bust, legend, etc) stretching. If you measure this global expansion factor of the design on the brockage vs non-brockage side, then use that to calculate where the bottom beaded edge would be, it is indeed off-flan.

I think maybe what's happening here is that the brockage "punch" (coin) design itself is already stretched relative to the design on the die that struck the other side, and maybe the outward vs inward force of a punch vs die is having little effect (except maybe some localized device-by-device stretching - need to check if local expansion factor is same as global expansion factor). It seems that the flan flattening/stretching that occurs due to striking is not just extruding metal from the edges of the dies, but is rather also stretching the whole of the struck coin (maybe some very short lived inertia/metal-flow after the strike?), and the brockage side thus appears stretched and missing edge detail because it was struck with this stretched "punch" rather than the original sized die that struck the other side (but of course in a case where the flan had been larger relative to the die, the border would still appear).

As for level of detail on both sides, it looks about the same to me subject the perceptual limitations of the different shadows due to the convex vs concave designs.

Ben

Offline curtislclay

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Re: Strange coin of Constantine II ??
« Reply #12 on: December 15, 2008, 06:18:21 pm »
I think I see the question now: basically, you are asking why the types on the incuse side are often substantially larger than those on the positive side.

I think Ben's explanation doesn't take account of the major component:  it's the preceding coin that adhered to the rev. die that expands as it functions as a rev. die and is crushed between the true rev. die on the one hand and the new blank on the other!

That expansion begins as soon as the portrait, the area of highest relief on the coin, begins to be sunk into the new planchet.  By the time the legend and border of dots make contact, the coin functioning as rev. die has already expanded some and pushed the border of dots beyond the edge of the new planchet!

I think it was Doug Smith who brought up an interesting point in a previous discussion of this matter:  since brockages with expanded incuse sides are quite common (see the two examples below from CoinArchives), where are all those ordinary coins with expanded obverses that must be predicated to have served as their rev. dies?  My answer is that they must be out there and that die studies of coin types that were frequently brockaged will eventually identify some of them!
Curtis Clay

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #13 on: December 15, 2008, 07:04:35 pm »
Alright Curtis, I was waiting for that.  If there is an expansion of the "die" coin preferentially based on the highest parts hitting the new coin first, then there would be some noticeable distortion of the design, much as the DIVO TRAIANO coin seems to show.  The "die" coin would deform outward from the center, but the letters would not be deformed as quickly, so they would not show the same proportional size difference that the bust does.  Both Constantine II coins show, and I think calipers would probably bear this out, the same expansion of the letters as the head with no deformation of the design at all.  Clearly, physics does not allow this.
Part of my problem is that these larger, yet still undeformed, portraits and letters show up on coins that I have problems with already.....as in I don't believe either Constantine II coin mentioned in this thread is authentic.  Neither have I felt any brockage with this large variation in size ( I have seen about 4 now) were authentic.  And it was not the brockage that made me worry, although it was always another piece of the puzzle.
Jeff Clark

Offline Heliodromus

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Re: Strange coin of Constantine II ??
« Reply #14 on: December 15, 2008, 07:48:11 pm »
Jeff,
Here's one of mine that shows considerable expansion that hopefully you'll not have any authenticity problems with!

I've included the larger pictures so anyone can easier make measurements if they wish.

The unstruck portion of the brockage side is considerably thicker than the struck portion.

Ben

Offline curtislclay

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Re: Strange coin of Constantine II ??
« Reply #15 on: December 15, 2008, 08:04:21 pm »
Jeff,

I think some expansion of the coin serving as rev. die would occur when its portrait entered the new flan, but MOST of its expansion would occur after its complete type and legends had sunk into that new flan.  Therefore the expansion would affect all details on the coin to the same degree, legend as well as portrait.

Physics, you say, will not allow the effects observed.  I would answer that the effects are plainly there, we know what must have caused them, therefore physics MUST allow them, no matter how one theorizes!
Curtis Clay

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #16 on: December 16, 2008, 09:52:55 am »
Ben,
Respectfully, whether or not your coin is good or not, it does not show the same expansion observed on the Constantine II piece.  The largest difference I could measure on yours was a 6% difference from the top ^ corner of the eye to the bottom of the ties at the back of the head.  From nose to back of the head on the Constantine II, there is a 15-17% difference.  And in fact, the distance from the edge of the largest bead at the top of the coin straight down to the top of Constantine's head is actually less on the brockage indicating that indeed the bead is somewhat larger as might actually be expected.  This brockage can not come close to explaining the problems of the other.

Curtis,
Also respectfully, I don't think we quite know exactly what occurred with these coins a few years ago and we certainly do not know what caused them on these Constantine II coins if indeed they are real.  You are beginning a circular arguement and it won't hold water unless it can be defined a little more clearly. 
What you are saying now is that the expansion occurred after the design sunk into the new flan...then why didn't the border beads, which hit before the letters, sink into any part of the flan?  You are now saying that before the "die" coin expanded, it transfered its image, then it expanded and its image expanded as well and the dots, which would have been there initially before the expansion, just fell off the edge of the new coin?
Jeff Clark

napki

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Re: Strange coin of Constantine II ??
« Reply #17 on: December 16, 2008, 01:23:17 pm »
Quote from: Jeff Clark on December 16, 2008, 09:52:55 am
I don't think we quite know exactly what occurred with these coins a few years ago and we certainly do not know what caused them on these Constantine II coins if indeed they are real. 

Brockage basically same in ancient mint as in modern mint. Sometime struck coin stick to hammer die (called "capped die") and strucked many coin before discovery. Each striking make coin on capped die more flattened and expanded because it same softness as new blank, not hard like die. So first brockage created have fairly sharp image pretty close to original. 20th coin struck have much more expanded imprint on reverse.

Brockage and related errors very well understood by mint worker or error expert like Mr. Fred Weinberg. Should check general error coin sites or books. Only difference in modern is machinery and retaining collar.


Offline Heliodromus

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Re: Strange coin of Constantine II ??
« Reply #18 on: December 16, 2008, 10:57:06 pm »
Thank for that napki - I went and did some further reading up on the brockage-capped die continuum.

I think that one difference between brockages/capped dies in ancient and modern times is that the capped die (stuck coin) would usually, if not always, have been detected earlier in ancient times since it was a manual rather than unattended process, and therefore in ancient coins there are probably more early stage brockagessharp and same sized, or moderately enlarged, and less of the later much enlarged and distorted brockages and few if any of the late stage true capped die stikes (& die caps) where the die cap has worn so thin that an indistinct positive image is actually struck through it. The spreading die cap does of course neatly explain why the border/etc gets lost as the cap size gets enlarged relative to the fresh flans it is striking.

I found a great image of a die cap here:

http://minterrornews.com/glossarycappeddies.html

Ben

Offline Heliodromus

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Re: Strange coin of Constantine II ??
« Reply #19 on: December 17, 2008, 12:35:57 am »
I did find one coin on coin archives that might be a die cap (i.e have been used to strike an obverse brockage) - at least it exbihits the gross characteristics of what I would expect one to look like. I couldn't find enough comparison pieces to indicate if the diameter is slightly larger than expected for the weight, as would be expected.

http://www.coinarchives.com/a/lotviewer.php?LotID=104750&AucID=111&Lot=1259

Note of course that we wouldn't expect an ancient "die cap" to become cap/cup shaped since there's no collar and the die seems to typically extend well beyond the engraved border which would cause the "cap" to remain flat.

Ben

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #20 on: December 17, 2008, 12:11:36 pm »
Yes napki, thank you for the name of a seller that actually shows a few of the modern bockages and the effects.  Mr. Weinhard's site has a number of these die capped stuck coins for sale and the effects are just as one might expect. 
http://www.fredweinberg.com/inventory/categorylist.asp?t=c&ID=12
The Malayasian coin in particular shows the type of distortions that one would expect early in the series of repeated strikings.  Their is loss of detail, the date has bent into a curve and nothing is retained of the original dimensional integrity.  Even the 0s in the date are slightly different in size and shape from eachother.
These coins definitely seem to me to show exactly what I am trying to say...  there is a required distortion and loss of detail when you expand with an uneven force that occurs when an uneven surface hits a flat one.  Again, simple physics born out by actual coin pictures.
Jeff Clark

Offline Heliodromus

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Re: Strange coin of Constantine II ??
« Reply #21 on: December 17, 2008, 12:54:49 pm »
Jeff, I don't think that's really a fair comparison - the Malaysian coin is not only a die cap in addition to a brockage, but also the brockage side was evidently (degree of expansion) struck with quite a late stage die cap on the lower die. It's also not at all obvious that the linearity/radiality of the forces on an ancient die cap would be the same as those on a modern one where there's the additional distortion of being forced up around the die (unless there's any proof that this also occured during ancient coin manufacture).

It seems the understanding of the die cap incrementally spreading on successive strikes as more than one brockages are struck by it answers your question of why brockages show enlargement and missing edge details (why the whole design doesn't transfer). The issue of distortion, or the lack of it, possibly remains, but I think a large part of the answer - if not indeed all of it - is given by the differences in ancient vs modern practices and that ancient die caps were almost certainly caught earlier - certainly there no recorded cup-like ancient die caps that I'm aware of, which should serve as warning that a direct comparison with modern coins likely isn't warranted.

Ben

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #22 on: December 18, 2008, 11:49:04 am »
Ben,
To be honest, I had not even thought of these ancient brockages as being the product of more than one strike!  It is amazing what help a little outside thought can be.
Of course, the reason I had not thought of these as strikes further down the line is that the amazing detail shown for some of these would not survive many strikes and certainly not when the flan is already expanding and the uppermost design, which hits first,  must preferentially expand...if it has the same ductility.  Perhaps they don't have the same ductility?
I also had not really understood the die cap issue....and more importantly have another strange question.  If a die cap covers or gets stuck on die A, it would normally be struck on the other side with die B...correct?  Now, die A comes down on a new planchet still holding the die cap which has the struck die B side toward the plancet and you strike a new coin with die B and incuse die B don't you?  What mechanism creates the die cap with a die A and incuse die A brockage like these die caps show? Or is a die cap really a brockage rather than a die cap?  What am I missing that must be obvious here?
Jeff Clark

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #23 on: December 18, 2008, 12:00:40 pm »
Well, to answer my own questions on die caps, perhaps the brockage is the reason a die cap was created in the first place? 
A coin is not ejected from the stiking position, a new coin comes in, the force of the strike causes the coin to cap the die A and struck die A coin side hits the new planchet creating an incuse of die A which is esentially exactly the same as die A already should be.  You could then continue striking coins which were not brockages but were being struck with the incuse image of die A now on the die cap.  This certainly explains what I see on these die caps.
Jeff Clark

Offline Jeff Clark

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Re: Strange coin of Constantine II ??
« Reply #24 on: December 18, 2008, 05:55:42 pm »
It seems like we are bit played out on this issue?
I do have one more little factoid to consider with these expanding brockages.
It seems to me that the depth of the strike on the brokage side is greater, or certainly equal to the outward relief of the obverse.  I could see that happening on the first strike, but as successive strikes occur, which cause the expansion of the flan, certainly the depth of the relief must diminish accordingly. 
I do actually own one of these brockages and one time I attempted to measure that depth, but in the few minutes that I tried, I never quite got any device that would allow an accurate measurement.
Jeff Clark

 

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