The use of billon coins dates from ancient Greece and continued through the Middle Ages. During the sixth and fifth centuries BC, some cities on Lesbos used coins made of 60% copper and 40% silver. In both ancient times and the Middle Ages, leaner mixtures were adopted, with less than 2% silver content.
Billon coins are perhaps best known from the Roman Empire, where progressive debasements of the Roman denarius and the Roman provincial tetradrachm in the second century AD led to declining silver and increasing bronze content in these denominations of coins. Eventually, by the third quarter of the second century AD, these coins were almost entirely bronze, with only a thin coating or even a wash of silver.
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- Erik Christiansen, Coinage in Roman Egypt: The Hoard Evidence (Aarhus University Press, 2004) 135-141.