This coin should put the "misaligned pincer tongs" theory to rest

In the October 1992 issue of The Celator (p. 4), Marvin Tameanko proposed that the indentations on Roman provincial coins ("centration dimples") were the result of mint workers using pincer tongs to remove the flans from the furnace where they were softened prior to striking:


Wayne Sayles, in Ancient Coin Collecting IV: Roman Provincial Coins (pp. 130-131), considers Tameanko's theory to be "the most plausible."

Well, this coin in the Harvard Art Museum's collection should put that theory to rest once and for all.



There is clear evidence of rotation of the flan around a spindle, with a clear circular scratch around the dimple and also the mark of a point inside the dimple itself. See these close-ups:



This unequivocally disproves Tameanko's "misaligned pincer tongs" theory. Also see the coins @dougsmit shows at his page along with his thoughts about the dimples. I believe Doug also has examples of coins that were struck extremely off-center, such that large amounts of unstruck flan outside the coin's devices show concentric circular scratches consistent with something rotatating relative to the surface of the flan prior to striking.

This could either result from a stationary flan being smoothed by a bow-drill type of apparatus turning a blade or abrasive disk, such as David Sellwood advocates in the minting chapter of Roman Crafts (Donald Strong and David Brown, eds), or it could result from a flan being turned on a rotating platen while being smoothed by a stationary blade, as described here in this excellent article at the Classical Coins web page.

I would love to see examples of coins in your collections that clearly demonstrate evidence of this method of flan preparation.

 

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It seems farfetched to me that someone picking up a hot flan with pincer tongs would ever get anywhere close to the center. It also seems farfetched that misaligned tongs would pick things up at all, instead of flipping them away; if the flan were "sticky" enough that you could do this, surely the dimples would be distorted in an obvious way.

I'd have a lot more respect for a "theory" like this if the theorizer had tried putting together some aligned and misaligned pincer tongs, heating up some metal, and experimenting. With pictures.

 

There is no guarantee that the ancients always did it the same way all the time either.

 

..i'm from Missouri....

 

Show me!

 

BingO ^^

 

This illustration should appear in a high school physics text under the title "What's wrong with the lower picture?"

Jeez, you don't have to be Isaac Newton to recognize that the planchet would rotate in the bottom picture. Try picking up a rigid flat object with your thumb and first finger misaligned to understand the fundamental physics that disprove the second theory.

Well, most numismatists probably never took a physics course...

 

hey ..E=mc2!

 

Physics? What's that? I had a physical last year. Does that count?

 

I had never even heard of Tameanko's tong theory until now. Even if the pincers were perfectly aligned, I doubt you could put enough pressure on the coin to create such deep dimples.

 

That's a very legitimate objection to the tongs theory, and some have proposed that the tongs weren't used to carry the flans, but only to test them to see if they were soft enough to strike.

However, there are problems with that theory, too. @dougsmit mentions three:

"First it would seem that a flan made soft enough to be marked by the tongs would have been soft enough to have erased the marks when subjected to the much greater force of striking. Second, it seems odd so many coins are seen with a very distinct mark on one side and little or none on the other. If the purpose was to determine softness, it would seem the flan would have been equally soft on both sides. Finally, this theory fails to address either the concentric ridges or the dimples that show rotation. Misaligned tongs would hardly rotate so smoothly."

 

You beat me to it. Should be obvious to most that mis-aligned dimples = no rotation did or can/could occur. Still, they do seem to be some part of the flan preparation. What that was I have no idea, and I dont think anyone will ever know.

 

something put the dimples there, no doubt, and we'll have fun debating what it was since the coin making method has long been lost

 

I should qualify that evidence of rotation is clear on many examples (sometimes I fire off a reply assuming everyone knows whats in my mind. That can and has gotten me into trouble in the past!). Obviously this rotation could not occur in the Tameanko theory. Under just what circumstances it happened is the real question. I would have to assume that perhaps the flans were prepared one side at a time. This would account for proper rotation and also explain mis-aligned dimples.

 

I did not see this thread until my thoughts had been quoted from my page. I had heard of the Tameanko's tong theory but always considered it ridiculous.

There are two basic types of these dimples. I believe they were both made by the same tool. On the first below, the pins that held the coin held fast in the coin but rotated in the tool mount. The dimples are irregular.


On the other type, the pin held fast in the tool and rotated inside the coin making a dimple that was round and often striated. It is not necessary that every coin would show the same tpe dimple on both sides since we have to allow for things like how hard they pressed or even if both sides were trimmed by the same tool. Certainly not all had to be done exactly the same way. Coins like this were made for 500 years. Technology advances.

I had close ups of these pits on my webpage pit page that RC quoted. Thanks to him for reading that page. The matter is well treated on the Ptolemy page from which I lifted this image. The question is whether pin R rotated freely in the mount above it or stuck so it rotated in the coin below.

http://www.classicalcoins.com/flans7.html

 

I have a bunch of Ptolemy bronzes so I'm rolling in dimples

Here's one which is interesting because it looks like there is a raised circle around the dimple. Today I'll dig out the coin and see if it really is raised or if that is an optical illusion.


EGYPT. Ptolemy IV Philopater
221-205 BCE
AE36, 41.9gm
Obv: Head of Zeus Ammon right with ram's horn, wearing taenia diadem
Rev: ΠΤΟΛΕΜΑΙΟΥ BΑΣΙΛΕΩΣ, eagle with open wings standing left on thunderbolt, head right; Σ E between legs
Ref: Svoronos 1148? The diameter is smaller but the weight is similar
ex Professor James Eaton Collection

 

Thats an interesting page and shows the author put quite some time into the idea but it really is all wrong. So very wrong. His diagrams show that if this were how it worked the flans would be perfectly round. But we know this not to be the case. Yes, some would argue that striking the coin from the planchet after this process would put the flan out of shape. But we can see that this cannot be (especially so when looking at Ptolemaic coins of large thickness). I think the answer is somewhere in between. It started with one idea and ended with another.

My questions on the topic become more complex. Why prepare two sides of the planchet when one should suffice if assuming it was for weight only?

 

Samples shown show rounding off. Coins got reeding to cure shaving. Maybe this all is an aftermarket scam run by proto-mafioso.

 

The explanation on the http://www.classicalcoins.com/flans1.html website is the result of years of discussion and input from metallurgists and metal workers. It works just fine to explain everything I have ever observed on "centration dimpled" coins. There is no reason that it had to produce perfectly round flans - we can tell from the tool-marks around the edges and how they show evidence of "chatter" that the blade was "riding" around the edge and not cutting an edge in the manner of a solidly fixed tool on a modern turret-lathe. You can see where the pontils have been reduced, but not, necessarily, trimmed completely away, although the tool marks can be seen to go up and over the pontils.

Both sides needed to be faced as it was necessary to remove the slaggy crust and/or any sand or other debris which might be incorporated into the surface of the cooling metal after pouring. That nice, smooth flan-surface produced when any impurities and/or brittle, hardened metal had been planed away on those large flans would be ideal for striking with the least damage to the dies. It probably required a huge hammer - or possibly a drop-hammer - to strike the features onto those those 40+mm drachmae.

The whole "theory" of hot striking seems likely to originate from an expatiation of someone's observation of a blacksmith working red-hot (softened) iron or steel. Coin alloys do not have that same broad range of temperature between "solid" and "liquid". In iron, it's several hundred degrees, in silver or copper it's only a few degrees. It would have been impossible with the furnace technology available to heat flans to that narrow temperature-range and maintain it without melting them or allowing them to cool. Even if it were possible to heat-soften them in bulk and maintain that temperature range in the furnace, in the time it would take to grab one with pincers and transfer it to the waiting obverse "trussel"-die it would have cooled enough that any advantage gained by heating would be lost and the metal would be as solid as if it had started out cool. Even if there was some sort of quick "feeder" apparatus to deliver these theoretical heat-softened flans to the die, as soon as they touched the die it would act as a heat-sink and again, they instantly fall below the temperature at which heating might possibly do any good - plus, heating creates fire-scale.

That (cast) flans were heated before striking, however, makes sense. They would want to anneal the cast metal to relieve the stressed surfaces created by differential cooling of the flans and soften the metal pre-strike - but there is no reason the flans could not be left to cool completely before striking. In fact, they probably went from the annealing furnace to the "pickling" vat where the surfaces were acid-bleached and cleaned of any fire-scale that the casting or annealing processes may have left behind. Fire scale would have resulted in "strike-through" traces on the surfaces of the coins and would have made the dies wear out more quickly.

 

Thanks, @lehmansterms, for your excellent argument, even I can understand it. I didn't know about that difference between iron and more suitable coin metals. So, coins were not struck with heated flans.

I know only of two not too long periods in classical coinage that show the dimples. One period is that of the large Ptolemaean bronzes in the third and second century BC, and the other is the Roman provincial coinage of the first half of the third century, also in the larger coins (over 22 mm I would say). And often in the larger Provincial coins, there is no sign of a dimple. But I'm sure there has been research about the exact dates and places of the dimples, and that many of you know more about this.

By chance, I saw this coin today in an auction (I didn't bid for it). An AE of Valerian from the city of Nysa in Lydia weighing 8.52 gr., 30 mm, with a damaged dimple on both sides.