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I would like to understand how the Romans minted coins. Mining, smelting and refining are no mystery; I can envision ways in which uniform coin-blanks might have been made : but the big problems are (1) the striking of the coins themselves, and (2) the means of mass production.

The dies were small, and intricate in design, but what tools were used to shape them? Have any tools for die-sinking ever been identified and, if so, what were they made of? Was there any aid to vision? And what was the material of the dies? To withstand repeated hammering of bronze or silver, a die must resist wear and distortion (the stress in stamping gold is significantly less), so was there a hardening process?

And once all that has been settled, how was the necessarily prodigious striking rate achieved? Allowing that a blank stock sufficient to allow uninterrupted striking is plausible is one thing, but at, say one minute per coin, during twelve hours of daylight, one pair of dies would produce 720 coins per day, by which time the die might be quite well worn. At such a rate, to turn out a million coins would need 1,400 working days — and the circulation could actually run into billions of sesterces!

One reads of two opposing dies being struck with a hammer (there are even photographs of them), but I have never come across a believable account of the whole business. The industry would have been a large employer of highly skilled labour, but I can't find any discussion of it. Was there any way of increasing efficiency, in the way that (for instance) the spinning jenny revolutionised the textile industry?

I have already asked this question on the Latin language site, but to no avail. Over the years I've tried to discuss this with all manner of people who I thought might help, but few had paused to think it out. Maybe I've been asking (and looking) in the wrong places. Can anyone point me to ancient sources for solid information?

  • I don't have any sources, but I think it's apparent that it wasn't 100% done by hand. I think they must have had some kind of frame to hold the die steady. – Ryan_L May 10 at 14:09
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    The page How ancient coins were made may be of interest. In brief, there are no written records of how they made the dies from which coins were struck, and few survive archaeologically (most were probably destroyed when they became worn to prevent their use by forgers). We have dies in both bronze and iron. – sempaiscuba May 10 at 14:14
  • @Ryan It's not difficult to imagine something like a modern fly-press (with a lever system instead of a screw) to make a significant increase to output. However, I'm wondering about actual evidence! – Tom Cotton May 10 at 14:16
  • @sempaiscuba Thank you for that first reference. One particular difficulty I have is in believing that anything I've read so far, anywhere, has been written by someone with any knowledge of physical metallurgy. – Tom Cotton May 10 at 14:23
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    If you're interested in the the metallurgical aspects, try to get hold of a copy of 'Experimental Minting and Metallographical Analysis of Roman Silver Coins' by Lu et. al. – sempaiscuba May 10 at 14:35
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Question:
Roman methods for minting coins

Skilled labor jobs in Roman times were performed by master and apprentice systems.

I found this.

How Ancient Coins were Made

Coin Production.
Flans or blank coins were produced by cutting pieces off of bars and then hammered into shape. The flan could be used as is or placed in an oven until soft. then placed into two sided dies, either bronze or Iron dies were used depending upon the coin. Then a hammer was used to smash the dies to imprint the coins. A team of workers could produce 20,000 strikes (coins) per day. During the Second century about 17 million Roman denarii were issued each year.

Die Production:
The mystery is how Romans produced the dies because the coin production process would require new dies everyday. How did they get the portraits so uniform if a new artist was individually cutting each die?

Perhaps they used a die production method described by 16th Century Medalist Benvenuto Cellini who was the first to employ a screw press to minting coins.

How Ancient Coins were Made

  1. The central design is sunk in the dieblank, either by casting or hubbing.
  2. The legend is added by letter punches which are individually struck, perhaps using afixture to align them.
  3. The border is similarly added by punching dots around the legend.
  4. The completed design is hand engraved for touchup where needed, then polished

Or perhaps as the source goes on dies were produced by separation of work with the Masters completing the portraits and their apprentices following up with the engraving and boarders.

Sources:

  • As you point out, it's a master apprentice system. So the masters would be skilled enough to replicate the same image and presumably the apprentice at some point becomes skilled enough to do so as well. I would think that individual dies would be recut with the same design over the original until the die was no longer needed or too little metal remained to be recut. It's possible that apprentices/journeymen would do this work while the masters worked from stratch. – Daniel May 10 at 22:11
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The Roman's used primarily two methods for minting coins, hot pressing and cold pressing. And just as it sounds cold pressing involves striking the coin while its cold while hot pressing strikes the coin while it has been heated up to make it more malleable.

Dies were used to impress an image on the front and on the back of the coin. Greeks typically relied on the weight of a hammer to pound the image onto the blank, while the Roman's typically used a hinged die set that allowed simultaneous striking on both sides. After the coin was pressed it would go to another craftsman final touch ups.

As to how long the die would last, that has been estimated at around 30k strikes from this source.

How many coins could a die strike before it broke, or wore out? This vexed question is a source of endless debate. Dies typically lasted three to four months in heavy use. A die might last five years or more in intermittent production. One estimate, based on a specific issue of Delphi (338-333 BCE), is that an obverse die was good for 23,000 to 47,000 strikes, while a reverse die could sustain 11,000 to 28,000 strikes (Howgego, 32)

Many academics extrapolate the amount of total coins per set to the amount of dies they have been able to locate.

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I am not an expert on Roman mints and coins.

I do know that the Roman Empire contained many cities with their own governments and that many of those cities designed and issued their own coins.

And the imperial government also had a number of different mints in different cities.

You may have heard about the great emperor Aurelian https://en.wikipedia.org/wiki/Aurelian1 who reigned from 270 to 275 and helped to save the Roman Empire from the terrible Crises of the Third Century by defeating barbarian invaders and reconquering the breakaway Palmyrine https://en.wikipedia.org/wiki/Palmyrene_Empire2 and Gallic https://en.wikipedia.org/wiki/Gallic_Empire3 Empires.

According to the Augustan History:

There was also during the rule of Aurelian a revolt among the mint-workers, under the leadership of p271 Felicissimus, the supervisor of the privy-purse.142 This revolt he crushed with the utmost vigour and harshness, but still seven thousand of his soldiers were slain, as is shown by a letter addressed to Ulpius Crinitus,143 thrice consul, by whom he had formerly been adopted:

3 "From Aurelian Augustus to Ulpius his father. Just as though it were ordained for me by Fate that all the wars that I wage and all commotions only become more difficult, so also a revolt within the city has stirred up for me a most grievous struggle. For under the leadership of Felicissimus, the lowest of all my slaves, to whom I had committed the care of the privy-purse, the mint-workers have shown the spirit of rebellion. 4 They have indeed been crushed, but with the loss of seven thousand men, boatmen,144 bank-troops, camp-troops145 and Dacians. Hence it is clear that the immortal gods have granted me no victory without some hardship."

http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Historia_Augusta/Aurelian/3*.html4

142 This revolt is described also in Aur. Victor, Caes. 35.6; Epit. 35.2, and Eutropius, IX.14. According to these authors, the mint-workers, who, with the connivance of Felicissimus, had adulterated the metal appropriated for the coinage, fearing punishment, broke out into open war. It would appear that they had been keeping a part of the silver that was to have been used for the billon (i.e., adulterated) coins. Though the number of soldiers said to have fallen is, of course, greatly exaggerated, a battle seems to have been fought on the Caelian Hill, near the mint, which was on the Via Labicana. The date is uncertain; it may have been on the occasion of the German invasion of 270‑271 (see c. xxi.5) or in 274, just prior to the reform of the currency (see note to c. xxxv.3).

http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Historia_Augusta/Aurelian/3*.html4

So the mint in Rome was so large an establishment that the revolt of the mint workers had to be crushed by the army and was recorded in the few historical sources for that era.

This shows that Roman coin production was a large scale industry.

  • I suspect the cast majority of that organization was manual labour tasked with supplying firewood for the smelting operations. Cutting wood before the 20th century was always very labour intensive. – Pieter Geerkens May 10 at 16:22
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    @ Pieter Geerkens Wouldn't most of the firewood for the mints be supplied by woodcutting operations in forests outside of the cities that the mints were in? Therefore most of the woodcutters and many of the wood transporters would not be based at the mints or form part of the large mint organizations within various cities. – MAGolding May 10 at 16:32
  • @PieterGeerkens While the equivalent of stokers would be important, there are all manner of tasks for an industry like this. Who made the metal sheets, cut out the blanks and every step requires transportation to/from the factory and within. Did they use their own carts or was that subcontracted? You'd have specialists who cut the dies and probably designed them too producing multiple copies for mass production. – Daniel May 10 at 21:58

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