Debasement

Starting with Nero in AD 64, the Romans continuously debased their silver coins until, by the end of the 3rd century, hardly any silver was left.

A debasement of coinage is the practice of lowering the intrinsic value of coins, especially when used in connection with commodity money, such as gold or silver coins, while continuing to circulate it at face value. A coin is said to be debased if the quantity of gold, silver, copper or nickel in the coin is reduced.