Fourrée

Cicero mentions that M. Marius Gratidianus, a praetor during the 80s BC, was widely praised for developing tests to detect false coins, and removing them from circulation.

Gratidianus was killed under Sulla, who introduced his own anti-forgery law (lex Cornelia de falsis), that reintroduced serrated edges on precious metal coins, an anticounterfeiting measure that had been tried earlier.

The most common method for producing a fourrée was to take a flan of copper, wrap it with silver foil, heat it, and strike it with the dies.

Exposure of the deception was often due to wear at the high points of the coin, or moisture trapped between the layers that caused the foil to bubble and then break as the core corroded.

In peripheral regions, even cruder counterfeits might pass: in the Viking-age site in Coppergate, in York, a forgery of an Arab dirham was found, struck as if for Isma'il ibn Achmad (ruling at Samarkand, 903-07/8), of copper covered by a once-silvery wash of tin.

During the Crisis of the Third Century, constant wars required a lot of coins to be produced, leading to heavy debasing of precious metal coinage.