A gold coin of a 'new' Roman emperor, Sponsianus

[Molinari]

Is the silver coin accounted for or lost?  I would like to see it too.

[Din X]

I have looked again at the article.

That there are some encrustrations  (wax and or dirt?) on them is not really proving anything you can find as far as I can tell based on pictures at least optically similar or identically looking encrustrations on many proven fake coins.

You can make encrustrations and dirt stick on coins and it is done by forgers for a long time. What are the encrustrations really proving?

Assuming  the encrustrations are containing earth/soil can they be traced to a very specific area in Romania, earth/soil can be very different in different countries and areas, so the earth/soil composition and Isotopes of elements could allow to determine the area where the earth/soil is from.

If there would be actually crytals of minerals visible we could check if they were produced artificially (finer structure because muuuuch faster growing under high temperature), or natural rough growing structure due to very low growing und normal temperature.


If there would be for example Malachite crystals with rough structure present on the coins, then we have only 3 possibilities:

1. coin is authentic
2. forgers sticked or glued them on the coin
3. or it was overstruck on an authentic coin with Malachite crystals (generally we should see if a coin was overstruck)

Malachite crystals with rough structure can not be produced artificially as far as I know, I have never seen or heard about that.

 
The surface of the coins is not as found anymore and the convervation with shellac resin and possibly other convervation methods could have influenced the result of surface analysis.
And the wax remains on the Sponsian coin could influenced the surface analysis too, if there is still a thin wax layer present on some areas.
And if chemicals were used for cleaning they could have affected due to chemical reactions the encrustrations too or if there are still traces of chemicals present. It seems like they were at least cleaned  with soap.


"Analysis by r-FTIR (see S.6.5.2 in S6 File) confirmed this as shellac resin, a substance that is known to fluoresce strongly"

"(GLAHM:40333) also fluoresces in white (Supporting Information S.2.6) and was confirmed to be wax by r-FTIR "

"The picture is further complicated by the presence of an organic compound which is likely calcium distearate, possibly from soap used to clean the coin (albeit not very effectively). Similar results were obtained from all the questionable coins. "

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0274285

[Molinari]

Thanks for this.  I believe the study claims that there is indeed a layer of crystalline silica that have formed over the deposits, consistent with the ancient examples they examined, and there is no evidence they are glued on.   

[Din X]

Thanks for this.  I believe the study claims that there is indeed a layer of crystalline silica that have formed over the deposits, consistent with the ancient examples they examined, and there is no evidence they are glued on.

I dare to ask, if it is not possible that this layer is related or the result of cleaning (they seem to be clean with soap at least) or chemical cleaning or from conservation with "shellac resin" ("confirmed this as shellac resin") or other conservation methods?

They confirmed that there are traces of "shellac resin" likely for conservation purpose and I can not understand this, gold is a very noble metal and has a very high resistance against acid and oxidation, there is no need to conservate gold coin and especailly not with "shellac resin". Have gold coins been conservated with "shellac resin" in the past?

And is it really clear that such crystalline silica can not be synthesized artificially? 
(I would like to have an analysis of the encrustrations on fake coins and a comparision with the encrustrations of the Sponsian.)

[Molinari]

You might be interested in the technical analysis that accompanies the paper--it is far beyond my knowledge base but there are some 150 pages of test results done on the coins. 

The author's claim they do not know if the crystaline layer can be produced artifically, and point to this as an area for further study (they claim there are no studies that indicate it can be produced).  But they maintain that an 18th century forger wouldn't know how to do that, or bother doing it. I'm not sure about that--as Mac indicated, never underestimate a forger. But if he were that good, why make such a lousy fake?

For me, if the encrustations can be proved fake, the entire case falls apart, because then the preponderance of evidence clearly points to fake, no matter how plausible the rationalizations are.

[Molinari]

A video from the authors--skip to the part (20:44) he talks about the encrustations:

https://www.youtube.com/watch?app=desktop&v=m7fM7GLcKcQ

[Pharsalos]

A silver ‘Sponsian’ is plated in an 1886 Adolph Hess auction (lot 161): https://archive.org/details/gri_33125010660690/page/6/mode/2up?q=Sponsiani
Hess (edit; actually ‘P. Joseph’) thought the piece may be genuine and gives an interesting commentary. It appears though the paying public didn’t agree and the lot was returned?

Below a comparison of the gold Sponsian piece from Brukenthal with the silver Hess lot.

Online English translation of the German lot description:

“Sponsian. IMP SPONSIANI head r. with Zackeukrone. RV. C AVG (Caius Augurinus). Two men on either side of a pillar on which a statue stands. AR Similar to C Bd. IV., 8. 231, No. 1 described piece in gold of the Vienna Cabinet. S.GE.

This piece has not yet been found in silver, and Sponsian is only known by the golden coin in Vienna. Coins of such extraordinary rarity as these are always in doubt and these would never be completely lifted even by the guarantee of the expert. Therefore, I just want to discuss the pros and cons and express my point of view. The piece is cast, the casting pin is clearly visible, since it is only slightly removed. The edge is not at right angles to the picture surface, but is pointed, as if the two shapes had not completely closed on the sides facing each other, but still left some space.

As a rule, it is considered that cast silver coins of the Romans from the time in question are unworthy. I am convinced of the opposite test and consider this piece to be worthy. A forger would have tried to make his work as similar as possible to the known genuine coins, so carefully removed the casting pin and also made the edge more smooth. The model of the modern counterfeiter should have been the drawing: with Cohen; however, our piece does not agree with this so completely that an imitation is to be thought of: it seems to me to have the Roman drawing style to a higher degree than Cohen's illustration, although the differences are unlikely to be describable. If I now refer to the well-known Trier find of clay forms from terra sigillata, the key to determining the method of production of our denarius could probably be given. I think of the course of the matter like this: when you were in Transylvania — there our silver denarius was found like the gold ones of the Vienna Cabinet, by Dr. Missong was purchased and then transferred to the collection of Herım Theodor Rohde — whom Sponsian, probably the leader of an army, proclaimed emperor, they did not immediately have the necessary material or time to cut stamps; they made molds from terra sigillata and poured silver into them. Our piece looks as if it was made in a slightly bent form during drying or firing. An old forger would have the most common coins. and low-grade silver is used or a piece of base metal is only surrounded with it. A modern forger would have had to use either Cohen's drawing - and this is untrue according to the above — or the golden copy of the Vienna Cabinet, and the latter is probably the least acceptable. It therefore seems to me that there is no reason at all to consider our silver denarius to be fake. But no one could give an unconditional guarantee.”

[n.igma]

I think it is worth considering the scale of what is being called 'encrustation'.

Review the images in the paper all of which have a scale bar. Most of what is analyzed are 5-100microns in size (and remember a micron is 1 millionth of a meter or one thousandth of a millimeter). With this dimension in mind, it is evident that what is subject to analysis are better described as surficial material rather than encrustations - this raises the issue of post recovery handling and storage environmental contamination of surfaces, something to which all the material was subject in the last 309 years.

The argument put forward is that these are soil deposits predating cleaning and 300 years of handling and storage - maybe, maybe not.

Moreover, if we take the argument at face value the underlying unproven assumption for 'authenticity' is that these micro-deposits on the surface can only form during extended period of burial. Yet the binding colloidal silica is capable of development on surfaces in soil in a matter of months - it is an active issue in the matter of iron corrosion of iron and associated scale development on iron and silica is an important natural component of ground and surface waters. 

Having stated that 'The silica is good evidence that the soil deposits formed in situ, i.e., they were not artificially applied, and there is no evidence of any organic glue.' the authors then state 'How long the questionable coins were buried for is difficult to estimate given the lack of comparative data.' from which the the proponents of the authenticity then move to state 'We must, however, allow time for the wear and burial described above. We are unable to devise any remotely plausible scenario that can account for the wear patterns, overlain by cemented earthen deposits, other than that they are products of antiquity.' 

All this in the absence of comparative data, knowledge of the rate of colloidal silica deposition in various near surface groundwater chemistry environments and in the absence of full consideration of the consequences of the last 300 years of storage and handling on the surface chemistry of a small group of coins in the Hunterian. The latter is a closed sample and uniformity among the coins in it is no surprise so the arguments based on this uniformity are circular in the absence of external calibrations and controls. Clearly there arise a few methodological issues in this approach.

And this is before considering the issue of wear as defined by the authors - almost all sub micron scale!

 

[Din X]

Briac

Had posted to numismatikforum the book where you can see more of the fakes including the medaillons and republic fakes.
I made a screenshot of the plate.

 "Blätter für Münzfreunde" 1923

https://drive.google.com/file/d/19_4hf9NVFLWkUGzLucDsapktTHzGM1Nd/view

I add a picture of another Sponsian Künker Auktion 226 Los 1091

And pictures of the one in muzeul National Brukenthal

[Molinari]

I think it is worth considering the scale of what is being called 'encrustation'.

Review the images in the paper all of which have a scale bar. Most of what is analyzed are 5-100microns in size (and remember a micron is 1 millionth of a meter or one thousandth of a millimeter). With this dimension in mind, it is evident that what is subject to analysis are better described as surficial material rather than encrustations - this raises the issue of post recovery handling and storage environmental contamination of surfaces, something to which all the material was subject in the last 309 years.

The argument put forward is that these are soil deposits predating cleaning and 300 years of handling and storage - maybe, maybe not.

Moreover, if we take the argument at face value the underlying unproven assumption for 'authenticity' is that these micro-deposits on the surface can only form during extended period of burial. Yet the binding colloidal silica is capable of development on surfaces in soil in a matter of months - it is an active issue in the matter of iron corrosion of iron and associated scale development on iron and silica is an important natural component of ground and surface waters. 

Having stated that 'The silica is good evidence that the soil deposits formed in situ, i.e., they were not artificially applied, and there is no evidence of any organic glue.' the authors then state 'How long the questionable coins were buried for is difficult to estimate given the lack of comparative data.' from which the the proponents of the authenticity then move to state 'We must, however, allow time for the wear and burial described above. We are unable to devise any remotely plausible scenario that can account for the wear patterns, overlain by cemented earthen deposits, other than that they are products of antiquity.' 

All this in the absence of comparative data, knowledge of the rate of colloidal silica deposition in various near surface groundwater chemistry environments and in the absence of full consideration of the consequences of the last 300 years of storage and handling on the surface chemistry of a small group of coins in the Hunterian. The latter is a closed sample and uniformity among the coins in it is no surprise so the arguments based on this uniformity are circular in the absence of external calibrations and controls. Clearly there arise a few methodological issues in this approach.

And this is before considering the issue of wear as defined by the authors - almost all sub micron scale!

Thanks for explaining this.  So based on your analysis, a forger could have buried these for a short time and the smallest particles of dirt that remained would have developed the thin layer once re-exposed to the air?  I think Din X’s comment is relevant here, however, that such dirt would rub or wash off very easily, and remnants of what appears to be soap were found.

[SC]

I think, and I am no expert, that when you speak of surfical material on the micron scale you don't even need burial.

A century or two of dust, airborne particles, cigarette smoke, coal smoke, etc could easily explain such material. 

Now maybe all those possibilities have been eliminated, but the "lack of comparative data" makes me wonder.

SC

[Molinari]

I believe the ‘encrustations’ are clay and quartz, dirt basically, and show the same composition as ‘encrustations’ on authentic coins.  Lloyd, do you know which was the largest of these dirt deposits?  I feel like I can see some on the Sponsian type with the naked eye so presumably much larger than the ones you mentioned.

[*Alex]

In the aftermath of Pearson's analysis, several researchers have criticized the study and its conclusions. In an article for the Times Literary Supplement, Mary Beard suggests that the unusual features of the Sponsianus coin are better explained by its being an eighteenth-century forgery. Richard Abdy, the curator of the collection of Roman coins at the British Museum, condemned the study, stating "they've gone full fantasy." In the Antigone Journal, Alfred Deahl also argues that the coins are forgeries: he cites the unusual weight of the Sponsianus coins, the poor lettering and use of the genitive instead of the usual nominative case, the highly irregular casting process used to produce them, the imitation of a republican reverse, and the oddness of the other coins purportedly found in the same hoard. These doubts are echoed by Aleksander Bursche and Kyrylo Myzgin, who add that the very early finding and low gold content may count against the coins' authenticity. Alice Sharpless from the American Numismatic Society summarized criticism of the Pearson study by writing "the evidence of wear and of surface deposits cannot be shown conclusively not to have occurred in the modern period [...] Unless further study can provide more certain answers, it seems that these coins should continue to be regarded as modern forgeries."

Pearson's study has also attracted significant attention from Romanian numismatists and classicists. Emanuel Petac, President of the Romanian Numismatic Society, stated that the coin "has nothing to do with the Roman world." On the basis of the design, which he characterizes as rudimentary and bizarre, and the inscription, he concludes that the coin could not have been minted by an emperor. Petac notes that the legend irregularly excludes his praenomen and cognomen, or whose son or grandson he is. Another Romanian academic, Florian-Matei Popescu, highlighted the lack of written attestations of Sponsianus or his name—though the name Sponsianus is attested in the Roman world in inscriptions, these are very rare. Popescu argues that if the coins are real, which he deems unlikely, they date to the reign of Philip the Arab, who opened a mint in Dacia making low-value bronzes to pay the army.

I agree with all the experts above and for me this subject has now run its course and I have little or no more interest in Pearson's evidence than I have for the evidence  for the existence of the Loch Ness monster.

Alex

[Kevin D]

Is the silver coin accounted for or lost?  I would like to see it too.

I don't know the silver coin's status.

Regarding the 'gold' examples, there has been recent research published (see 'White Gold') on surface enrichment of ancient gold and electrum coins. When this occurs naturally, it is caused by removal through corrosion of the silver or copper alloy at the coin surface over time. Reportedly, some mints enriched the surface of their coins artificially, presumably in order to give them a better (more golden) appearance.

If an analysis of the gold/electrum coins in question showed no difference between the surface alloy and the core (bulk), it would not necessarily condemn them as fake, but if there was a marked difference between surface and core (bulk), with the surface having a higher gold content, it might point to an ancient coin. The forgers of the early 18th century might not have known of this coin surface enrichment (natural or artificial), as it seems to be a more recent discovery.

[Molinari]

I believe the process you are describing is called depletion gilding, and that the Etruscans had been using it on their jewelry from at least the 5th century.  I didn’t know early electrum used that process but that is very interesting. 

I have a friend who is a jeweler and he might know if that technique was known in the industry in the 1700s.

[n.igma]

I believe the ‘encrustations’ are clay and quartz, dirt basically, and show the same composition as ‘encrustations’ on authentic coins.  Lloyd, do you know which was the largest of these dirt deposits?  I feel like I can see some on the Sponsian type with the naked eye so presumably much larger than the ones you mentioned.

Observation 1: we should not confuse common garden variety dirt accumulated over the last three centuries with encrustion - unfortunately the authors don't make this distinction and make no reference to cleaning the coins of dirt (as opposed to encrustation) prior to analysis.

For example the statement Gypsum occurs atop the larger earthen deposits, sometimes in association with potassic sulphates, which may be jarosite and/or syngenite (see discussion above). Gypsum and jarosite are well-known oxidations products under acidic aqueous conditions of soils originally containing disseminated pyrite and calcite [69, 70]. Syngenite, although less common, has also been observed as a surface weathering product in association with these other sulphates [71]. These observations demonstrate that the earthen deposits formed in an anoxic environment and were subsequently exposed to air. 

Now guess what gypsum is? Plaster of Paris by another name - CaSO4.nH20! 

Do you not think that over three centuries (prior to the invention of low cost photographic reproduction) these coins were not subject to multiple episodes of reproduction by plaster of Paris casting from impressions of the coin in clay, potentially resulting in the transfer to the coin surface of a residue of clay, gypsum and even fine quartz (SiO2) on the interstices of the surface of the coin? A messy process of mold preparation via impression of the coin into clay (Plasticine today) followed by mixing of plaster to pour into the mold(s) accompanied by the potential transfer in succession of clay minerals, gypsum dust and plaster to the coin in its handling during this process - layer on layer at the micro level.

Not to mention the multiple handling of the coins by many dirty fingers etc over three centuries, with the potential transfer of an endless variety of dirt, inorganic and organic residue to the coin surfaces.

Observation 2: the EDX analysis gives elemental not mineralogical composition. The latter might be inferred from the former within a certain degree of uncertainty. But look at what is analyzed in each case few microns wide and 1-2 microns deep (images below), from which sweeping inferences are made as to the entirety of the 'encrustation' which is clearly a composite of material and layers a large part most likely from three centuries of accumulated build up dirt from the handling and storage environment.

Observation 3: Silica (SiO2) comes in many forms dependent on the temperature and pressure of formation. Crystalline forms such as Quartz originate in a higher temperature and pressure environment, micro crystalline forms (e.g. chalcedony) precipitate from silica rich solution at low temperature and pressure, while amorphous, non crystalline, forms (e.g. opal) are colloidal deposits from groundwater at near surface temperatures and pressures sometimes associated with biological action (e.g. plant growth, worm excretions etc) or from marine organisms in the marine environment.  This is a non-technical and incomplete summary of a complex geohemical and mineralogical assemblage and phenomenon that needs to be understood in determining the merits of the inferences derived from the EDX and other analysis. Very fine quartz dust abounds in dirt by the way - you probably have some on your fingers at this moment. 

Observation 4: bury your coins for a couple of months below the water table in particular and the colloidal deposition phenomenon described above will occur on metal surfaces and the micron scale and probably even more extensively dependent on groundwater, soil chemistry and biological activity.

For me, if the encrustations can be proved fake, the entire case falls apart, because then the preponderance of evidence clearly points to fake, no matter how plausible the rationalizations are.

The ‘encrustation” evidence and the methodology employed in the analysis and interpretation of the significance of the ‘encrustations’ is problematic at best and certainly inconclusive.

Extraordinary claims, require extraordinary evidence and what we have is anything but extraordinary and conclusive evidence.

Put another way, Laplace's principle, which says that “the weight of evidence for an extraordinary claim must be proportioned to its strangeness”

I rest my case.

[Molinari]

You make a strong case!

[Kevin D]

I believe the process you are describing is called depletion gilding, and that the Etruscans had been using it on their jewelry from at least the 5th century.  I didn’t know early electrum used that process but that is very interesting. 

I have a friend who is a jeweler and he might know if that technique was known in the industry in the 1700s.

Depletion gilding might refer to an intentional act (versus a natural occurrence over time)?

Since the coins in question are cast, they would not have the high surface tension imparted in the striking process, so I believe they would be more susceptible to surface depletion/enrichment than would a struck coin. If the coins in question were analysed for this and found to have the same gold fineness on their surface as at their core (bulk), it might be problematic.

I hope I'm not too far off topic in this illustration of striking (minting) surface tension:

My tiny litra from Rhegion shows corrosion/depletion on the high points, but much less effected surfaces on the deeper points of the design. The deepest points of the design and the 'fields' of the coin represent the shallowest points of the dies, and this is where the surface tension from striking would be the greatest. As the metal flows and fills the die the force and thus the surface tension is decreased. Subsequently, the entire surface is subjected to the same environment, with the higher surface tension offering more resistance to corrosion/depletion. This is more evident with the coin in hand. A cast coin would offer less resistance.

[Molinari]

Oh now I see what you mean.  Thank you for clarifying.

[n.igma]

A silver ‘Sponsian’ is plated in an 1886 Adolph Hess auction (lot 161): https://archive.org/details/gri_33125010660690/page/6/mode/2up?q=Sponsiani
Hess (edit; actually ‘P. Joseph’) thought the piece may be genuine and gives an interesting commentary. It appears though the paying public didn’t agree and the lot was returned?

Below a comparison of the gold Sponsian piece from Brukenthal with the silver Hess lot.

Within the interpretative limitations imposed by the poor Hess auction image, a fair case can be made that the silver coin is from the same mold as the gold coin - note the cheek details in particular the sigmoidal gouge as well as the correspondence of the lettering in the legend.

This opens another problematic dimension to the authenticity argument as no Roman emperor ever struck gold and silver from the same dies, let alone cast them from the same mold for that matter.  So we have placed before us the proposition that the mysterious new Roman emperor Sponsian cast his 'prestige' gold coin in debased gold (high Cu content) and then produced cast silver coins from the same mold - it become more improbable with every coin that surfaces.

[Molinari]

I thought there were cases of shared dies between silver and gold during Imperial times?

[n.igma]

Standing back from the issue of authenticity it is multidisciplinary papers like this that pose a particular challenge for peer review.

To adequately review the Sponsian paper would require peer review not just by specialists in numismatics and history, but also discipline specific expertise in metallurgy, geochemistry, mineralogy and soil science, plus expertise in type specif analytical technique and analysis.

In this day and age, many academics at a well established university have access to advanced analytical tools such as SEM, FTIR, EDX but access and use does not necessarily confer highly developed expertise in the application of such technology, its limitations, and the interpretation of the results, within robust methodological and statistical practice.

Certainly the application of such techniques to a problem confers a perception of rigor in analysis, at least to the lay person, but this might only be a perception, with little or no basis in reality in the absence of total command of the technology and its application and interpretation in the broadest sense.

The paper was purportedly peer reviewed by three anonymous experts - which leaves it at least a few experts short of that required based on my thinking about the problem.

[n.igma]

I thought there were cases of shared dies between silver and gold during Imperial times?

I stand corrected if such is the case. But I am unaware of such instances.

[n.igma]

Final thought for those who are unconvinced of the relevancy of the 'encrustation' discussion - in relying on analytical techniques of extreme sensitivity at micron and submicron scale the issue of potential contamination must remain first and foremost in the consideration. The surfaces of these coins have been subject to three centuries of potential contamination since their purported exhumation.

Imagine if this was DNA evidence we were talking about (the sample contamination risks and exposure are identical) - those prosecuting the authenticity argument would would be torn to shreds by the defence based on the potential for and existence of sample contamination - it would fall well short of the test of 'beyond reasonable doubt' to the extent that no jury could ever find the coins authentic based on the 'encrustation' argument presented.

[Dominic T]

I thought there were cases of shared dies between silver and gold during Imperial times?

Two examples, the second one only for the obverse:
DT