I am having trouble finding information on this and I lack the knowledge to know how feasible or not this would be.

I'd like to know how perfectly round coins could be made in the early middle ages. Where minting was done by hammering bullion to a plate of a certain thickness first, then cutting it in circles, and then hammering these circles with the stamp.

The outcome would be a circular coin I am sure, but you also often see coins from the middle ages, or earlier, that have a more fluid shape than a perfect circle. I find a lot of sources that go about the creation of coins and the process of minting them, but not much about the end result or how 'perfect' or standardized the result was. I know coins would be weighed and tested against scratches on a touchstone for metal content/makeup and such, but I again find not much about the circular shape.

The reason I ask this is that I have made a sort of coin keeper for a kingdom. It is basically a wooden shaft with two rounded caps, of which one can be taken off. The coins are stacked onto this stick by a hole in the middle of them, this would be a snug fit. The idea is that the rounded caps have a standard size which would be the one most coins would have. Making it easy/ easier to see if a coin has been clipped.

  • $\begingroup$ (1) You can put the coins of a string through the holes in the middle; this is how they did it in China and countries influenced by Chinese culture. (2) They could have made them round, but they just didn't care. (3) To make the coin perfectly round all you need is a sturdy steel cylinder. Put the roughly round blank in the cylinder and whack it with the stamp; the blank will deform and take the inner shape of the cylinder. They started using this process in the late Middle Ages / Renaissance. $\endgroup$
    – AlexP
    Mar 31 at 12:54
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    $\begingroup$ @alex that gives a very predictable diameter and shape, but a not-so-predictable thickness, thus variable metal content. Only practical if a coin has designated value, rather than intrinsic metal value, as all medieval and ancient currencies did. $\endgroup$
    – PcMan
    Mar 31 at 12:56
  • $\begingroup$ @PcMan: Step 1: Cut rough blanks. Step 2: Make them of uniform weight. (First two steps were practiced since the antiquity.) Step 3: Stamp the coin. The only difference is that instead of stamping the coin free on the die, you enclose the die in a calibrated cylinder. That's all it takes. It obviously gives a perfect thickness if the blank has already been made to conform to the weight standard. $\endgroup$
    – AlexP
    Mar 31 at 12:57
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    $\begingroup$ Bear in mind that the reason Sir Isaac Newton invented milling is that people would shear off metal from the edges for its value while preserving the look of the coin. $\endgroup$
    – Mary
    Mar 31 at 13:14
  • $\begingroup$ For a charming description of the process, see the entry Mint in The London Encyclopaedia volume 14, 1837, pp. 730 sqq. $\endgroup$
    – AlexP
    Mar 31 at 13:27

Where minting was done by hammering bullion to a plate of a certain thickness first, then cutting it in circles, and then hammering these circles with the stamp.

As far as I know, it did not exactly work it that way. The minting was done with a piece of metal of the requisite weight, put into a "coin anvil" maybe one inch deep. The anvil was often made up of a metal plate with a round hole, with an anvil plug at the other end. Then a percussor would be placed after the slug of metal, to close it in. Then the coinsmith would hammer on the percussor until, somehow (maybe from the sound? Or from experience?) he knew that it was enough. The anvil would be removed, and the newly minted coin would fall out.

With this method, though, having a hole in the middle of the coin seems unlikely. Chinese had square-holed coins (I have several XVIII century ones) but they were casted, not hammered.

One of the most interesting ways of "counterfeiting" money, used usually against gold because of its ductility, was to place the coin between the coin anvil plug and the percussor, without the metal plate in which the coin anvil should have gone. By carefully placing the three pieces so that the coin design would fit, and not be damaged, and hammering again, the two faces of the coin would squeeze together, and a "ring" of precious metal would form that could then be shaved. The coin would appear normal, but would be less thick. This method might also probably defeat the diameter-checking trick you designed.

However, this was only to scam people on the street - any banker would have checked the coin's weight, and in some cases (this was surely done in Venice in the 1500's) its density, using Archimedes' water-displacement method. There was also a recommendation to do the checking on the largest quantity of coins available, to increase precision (there were ways of "whipping" or "dusting" the coins to retrieve the precious metal dust, and you could remove up to a waterdrop's worth of metal before testing on a single coin would give you away).

Worn-out coins were re-melted and re-minted into properly-sized pieces; there was no difference between the worth of a coin and that of the metal it was made of (its "coin-ness" was only a sort of warranty seal on the metal).

  • $\begingroup$ This. The coins were exactly as valuable as the metal they were made of. Shape didn't matter. $\endgroup$
    – AlexP
    Mar 31 at 13:06
  • $\begingroup$ Thanks for the answer! As to where I got that bit from, it is from pages 4-5 from this PDF: library.oapen.org/bitstream/handle/20.500.12657/24386/… I'll wait another day but probably will accept yours as the answer. You gave me some more things to look up, like the water displacement method. My coins would also be the exact value of the metal they are made of (minus the seigniorage), but they would come in less valuable denominations that would see more widespread use than among bankers and such. People who would not be able to quickly weigh them $\endgroup$
    – Robin
    Mar 31 at 19:17

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