By Mike Markowitz for CoinWeek ….
BRICKS WERE PROBABLY the first mass-produced industrial product. Cast bronze arrowheads, produced by the millions, might well have been the second. But ancient coins were the most challenging mass-produced industrial product in antiquity.
The successful mass production of ancient coins required many advances in metallurgy and a complex division of labor. At Athens, the mint workers were slaves owned by the state. The mint stood near the southeast corner of the Agora (marketplace). At Rome, mint workers were mostly free. Originally located at the Temple of Juno Moneta on the Capitoline Hill, the mint later moved to a site 400 meters east of the Colosseum, where it remained until at least the late fourth century.
Some ancient coins were cast in molds, but most were “struck” by hand. Yet after centuries of archaeology and numismatic research, there are still plenty of unanswered questions about how ancient coins were made.
Bronze is easily cast in ceramic or stone molds. The crude and clumsy aes grave (“heavy bronze”) coinage of the Roman Republic (c. 290 – 220 BCE) was cast. The Etruscans and several other Italian peoples in the third century BCE also made cast bronze coins.
Bronze shrinks a small percentage of its original size as it cools, so successive generations of molds made from circulating coins (rather than a standard master) gradually became smaller and lighter.
Counterfeiters often used casting to copy official coins, and thousands of ceramic counterfeiters’ molds (perhaps deliberately buried to hide them from authorities) have been found, notably in Western Europe and Egypt. Two halves of a complete counterfeiter’s mold for a coin of Licinius (313 CE) brought US$225 in a 2009 auction.
Struck coins were individually hammered between dies that were carved or engraved by hand. A few hundred ancient coins dies have survived. Most of these are counterfeiter’s dies, since official dies were carefully controlled and melted down or defaced when no longer serviceable. Most early dies were made of high-tin bronze, a durable alloy of copper with up to 20% tin. Later, dies of iron and even hardened steel appeared.
A Roman counterfeiter’s bronze die for the reverse of a denarius dated to 136 BCE is mounted in a square iron shank 70 mm long. In a 2009 auction it brought $6,750.
At ancient mints, the first step in production was the preparation of coin blanks or “flans” from metal ingots delivered from the mines. Blanks could be cast in molds, chiseled from round bars, or cut with shears from hammered-out plates. Some blanks were struck cold (particularly pure gold and silver, which are relatively soft), while others were heated in a furnace before striking, and handled with tongs. The question of hot versus cold striking is a continuing controversy in classical numismatics.
A Roman denarius of 46 BCE shows some of the tools used in making coins. It was issued by mint official Titus Carisius. The reverse shows a pair of tongs and hammer flanking an anvil, above which is a round garlanded object sometimes identified as a punch die, but possibly a depiction of the protective leather hat worn by metal workers (an attribute of the god Vulcan). The head of the goddess Juno Moneta appears on the obverse. A well-centered, sharply struck example of this coin brought $3,000 in a recent auction; lower-grade examples typically go for a few hundred dollars.
Another controversy is the question of heads vs. tails – or, in technical terms, obverse vs. reverse. Normally the obverse die (“heads”) was fixed in a heavy anvil, such as a section of tree trunk, while the reverse die (“tails”) was embedded or welded to an iron shank that the mint worker held in his left hand to allow him to strike with the hammer in his right hand. It might take several blows to fully strike a coin, and if the die shifted between blows, we often see evidence of this “double-striking”.
The obverse die is typically carved in deeper relief, with the head of a ruler or divinity, while the reverse die was flatter, to better transfer the force of the blow to the metal of the blank. In some cases, however, it is not obvious which side was the obverse.
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).
Dies were sometimes kept in use after they cracked, and broken ones repaired and recut.
The artisan who engraved coin dies was called a celator in Latin. Some were exceptionally gifted artists who also engraved seals in hard stone. A number of famous Greek die engravers of the fifth and fourth centuries BCE are known by name because they signed some of their dies: notably Euainetos, Kimon, and Phrygillus. The extremely fine details engraved on the finest dies lead to speculation that some artists used rock crystal magnifying lenses, which are known to have existed in antiquity. On the other hand, the prevalence of spelling errors and letters engraved backwards on late Roman coins suggests that by that era some celatores were illiterate and semi-skilled.
A major controversy in classical numismatics centers around the use of “hubs” in the manufacture of dies. A hub is a specially hardened “positive” master punch that is pressed into softer metal to produce multiple “negative” copies for use as dies. A counterfeiter’s hub for the obverse of a denarius of Domitian as Caesar (c. 81 CE) appeared in a 2011 auction.
Most known ancient coin dies are in museum collections (though rarely on display), but some occasionally appear in major auctions, where they command high prices. A unique Byzantine iron die for the reverse of a follis of Justin I brought $15,000 in a recent sale. The cataloguer wrote:
This spectacular discovery of a very large early Byzantine coin-die is of major numismatic importance and of the highest rarity, and it is of the greatest interest since it allows an unprecedented glimpse behind the scenes of coin production.
The War of the Moneyers
One of the strangest episodes in the history of ancient coinage is a revolt by Roman mint workers that broke out in 271 CE early in the reign of the emperor Aurelian. Felicissimus, a treasury official, reportedly led the rebellion in which he died. According to the Historia Augusta (a notoriously unreliable source), seven thousand troops were killed in the suppressing of this Bellum Monetariorum (“War of the Coiners”).
One theory is that the mint workers had become accustomed to stealing a portion of the silver provided by the treasury for the thin silver coating surface on the antoniniani. When the harsh reformist emperor cracked down on this practice, they rebelled (Conway).
Exactly how these mostly copper alloy coins were “silvered” is uncertain. A minor amount of silver was mixed into the alloy. The silver might have been concentrated on the surface with careful heat treatment, or the blanks might have been “pickled” in strong vinegar to dissolve some of the copper, leaving an enriched layer of silver to be consolidated by striking.
Aurelian’s early coins from the mint of Rome are certainly of indifferent workmanship, but examples with partial silvering are common, and relatively inexpensive.
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 From which we get our word “money”; see https://en.wikipedia.org/wiki/Temple_of_Juno_Moneta
 CNG Electronic Auction 217, 26 August 2009, Lot 423.
 Steel is an alloy of iron with a small percentage of carbon, and often other elements. In antiquity steel was difficult to produce and highly prized. All modern coin dies, which have to withstand high-pressure machinery, are made of steel.
 CNG Triton XII, 6 January 2009, Lot 469.
 The numismatic term “flan” derives from a Latin word, flado, meaning “flat cake”. A delicious Hispanic caramel custard bears the same name.
 CNG Triton XIX, 5 January 2016, Lot 400.
 CNG Auction 105, 10 May 2017, Lot 1029.
 Numismatik Nauman Auction 51, 5 March 2017, Lot 609. Realized US$42
Becker, Thomas. The Coin Makers. Garden City, NY (1969)
Conway, Charles. “Aurelian’s Bellum Monetariorum: An Examination”, Past Imperfect 12 (2006)
Hill, George F. “Ancient Methods of Coining”, Numismatic Chronicle (1922)
Howgego, Christopher. Ancient History from Coins. London (1995)
Laing, Lloyd. Coins and Archaeology. London. (1969)
Meadows, Andrew. “Technology of Coinage”, Oxford Handbook of Engineering and Technology in the Classical World. John Peter Oleson (ed.). Oxford (2008)
Stannard, Clive. “Evaluating the Monetary Supply: Were Dies Reproduced Mechanically?”, Quantifying Monetary Supplies in Greco-Roman Times. François de Callataÿ (ed.). Bari (2011)
Vermeule, Cornelius, “Some Notes on Ancient Dies and Coining Methods”, Numismatic Circular. London (1954)
Ancient Greek Coins from Syracuse Currently Available on eBay