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Counterfeiting the Denarius and the Aureus: Capital Crimes in the Roman Empire

In the late Republic and early Empire, two Roman coins were made with a very high content of precious metals. The aureus was a gold coin, and the denarius was made with a silver content of up to 98% with the remaining metal being copper. The coins were about the same size, but the aureus was almost twice as heavy because gold is 1.84 times heavier than the same volume of silver. Twenty-five denarii were equal to one aureus. While the silver content of a denarius varied from 98% under Julius Caesar, 90% under Augustus, 80% under Trajan (AD 107), and down to 73 to 66% under Commodus (AD 180-192), the aureus remained essentially pure gold.

Since the cost of copper was only 1/100 that of silver, counterfeiters could make a huge profit by making a coin blank of copper instead of the denarius’s standard silver-copper alloy, applying a thin layer of silver or a high-silver alloy, and stamping a pattern like that of a genuine denarius into the silver. When copper is alloyed with silver, the color of the alloy is essentially the same as pure silver up to about 30% copper. This let counterfeiters make their fake coins look genuine, but it also allowed an emperor to decrease the real value of a denarius by reducing its precious metal content without it being obvious when one looked at the coin. Similarly, a coin blank could be gilded and stamped with the pattern of an aureus.

Legal production of coins during Republic and Empire

During the Republic, the responsibility for minting gold, silver, and copper-based coins belonged to the Senate. There was a single main mint in Rome at the Temple of Moneta. In the 2nd century BC, the Senate gave military commanders the authority to mint coins to pay their troops, so some coins were minted away from Rome. During the Empire, minting of gold and silver coins was restricted to imperial mints under the control of the emperor, although the lower value copper-alloy coins remained the responsibility of the Senate. The imperial mints were spread around the empire, and their locations changed over time.

Each time there was a change of emperor or some important event that he wanted to commemorate, new denarii and aurei would be minted with the portrait of the emperor on one side and a pattern on the back that served to promote the emperor’s authority and spread his message. Frequent changes of the back image and of the abbreviations on the front that described the emperor’s accomplishments and titles made it easy for someone to miss subtle differences between genuine imperial-issue coins and decent counterfeits.

Laws against counterfeiting

Counterfeiting gold and silver coins was considered serious enough to make it a capital crime. The first official law against it was established during the Republic in 84 BC, but the text of that law has been lost. However, in 81 BC, the lex Cornelia de falsis (Cornelius’s Law of falsity) declared that anyone who adulterated gold or made counterfeit silver coins broke the law. Anyone who could have prevented it and didn’t earned the same punishment as the counterfeiters.

The list of forbidden activities is quite explicit: anyone who adulterated gold and silver coins, washed them (to remove part of the noble metal), melted them, shaved them, corrupted them, defaced them, and rejected the coins stamped with the face of the emperor (except counterfeit ones), faced the penalty for counterfeiting. High-status Roman citizens (senators, equestrians) might be sent into exile. People born free were sent to the mines or were crucified. For gold coins, they might be fed to the beasts. Slaves and freedmen were subject to the “highest punishment,” which was often crucifixion.

The use of tin or lead to make coins that looked like silver was also prohibited.

How to counterfeit coins

There were several ways to apply the precious metal surface layer to the base-metal substrate. Since the denarius was roughly the wages for a day’s labor of a skilled worker, many more denarii than aurei were in circulation. That made it popular for counterfeiting. The metal used for the body of the coin was usually copper but sometimes bronze or lead.

One way of applying the surface silver layer was coating the surface with what was essentially a silver-copper solder. Another way of applying the silver was with a layer of silver foil that was attached to the surface either by soldering or by heating to form a mixed layer of silver and copper that melts at a lower temperature than either pure metal (a eutectic alloy). Other ways to apply silver include dipping the coin in molten silver, brushing molten silver onto the coin, or dusting the coin with powdered silver and heating it until the silver melts.

This type of counterfeit made from a base metal core plated with a precious metal is called a fourrée (derived from the French for “stuffed”).

Gold layers could be applied as thin gold foil, as with silver. Another technique popular in ancient times is called fire gilding. The gold was dissolved in mercury to make an amalgam with a buttery consistency. The amalgam was applied to the base-metal blank, and the coated blank was heated in a furnace to drive off the mercury, leaving the gold coating behind.

Blanks of copper or bronze were usually cast in round, flat molds. After the precious metal layer was applied, the blank was placed between two dies engraved with the front and back images of the coin and then struck while hot. Dies were made of either iron or high-tin-content bronzes. The obverse (front) die with the emperor’s portrait was stationary, and the upper die with the reverse pattern was hand-held. Each coin blank was placed between the dies, heated, and struck individually. There was no fixed rotation between the front and back patterns.

For lower value coins made of brass, bronze, or copper, a two-piece clay mold would be made from an original coin. Molten metal, usually a leaded copper alloy, was poured into the molds. After the metal hardened, the ceramic mold was removed and any slight projection on the edge where the metal entered the mold was removed.

The counterfeiting of gold and silver coins had extreme penalties applied by Roman law. Those same laws say nothing about coins made of copper or its alloys of brass and bronze. So, it appears counterfeiting of the lesser value coins that were not made in the imperial mints was not regarded as a serious crime. Low-value coins used for everyday purchases were often minted locally by cities and provinces to meet the high demand and frequent shortages. Adding counterfeits to this mix could even help reduce the shortage. In remote provinces, having an adequate supply of coins was a common problem. In Roman Britain, many of the coins in circulation were locally produced, including counterfeits.

How to identify counterfeit coins

There were several ways to identify a counterfeit coin. Shallow cuts to see if there was a base-metal underlayer, small areas where the silver or gold surface had broken and fallen away to expose the layer beneath, and sometimes weight were used. For an aureus, a counterfeit with a copper core weighed about half as much as a pure gold coin. For the denarius, depending on the fraction of silver in the official coins (which ranged from 98 to less than 70% before AD 200), a counterfeit coin in the hand felt about the same weight as the genuine coin. For someone not accustomed to handling genuine aurei frequently, even the lightness of a counterfeit aureus could easily go unnoticed.

For a short time at the end of the Republic, the edge of the denarius was serrated, both to show that the interior of the coin was the same as the surface and to show the edge of the coin had not been shaved. While serration was meant to be an anti-counterfeiting technique, counterfeiters simply serrated their products as well.

In Truth and Honor, the watchful eyes of Titianus’s business manager spotted counterfeit coins given to one of their ship captains in Carthago. Tribune Glabrio’s enthusiasm over assuming command of the Urban Cohort there with a serious crime to investigate drew Titianus’s warning to be careful. People who would engage in a highly profitable crime that carried the death penalty would do anything to keep from getting caught. When Glabrio arrived in Carthago, he learned how wise that warning was.

References:

Gaspar, Răzvan Bogdan. “Counterfeiting Roman Coins in the Roman Empire 1st-3rd A.D. Study on the Roman Provinces of Dacia and Pannoinia.” Journal of Ancient History and Archeology 2.4 (2015) 31-74. Print.
Roman laws and punishments for counterfeiting are summarized here, and Latin text of the counterfeiting laws and references to ancient sources are given. Many references to journal articles related to counterfeiting Roman coins are also provided.

Gorny & Mosch. “Damnatio ad Bestias, or: What Happened to Roman Counterfeiters?” CoinWeek. 7 May, 2015. Web. Accessed 2022.
<https://coinweek.com/ancient-coins/damnatio-ad-bestias-happened-roman-counterfeiters/>
This is a sales site with many images of the ancient coins they have for sale as well as various articles about ancient coinage (Roman, Greek, Biblical).