That’s true! I remember reading that this was happening in the late western period.
I guess the more things change ...
Some emperors were really diabolical about it. The mints would issue silver covered bronzes (fourée) that had to be accepted, but refused them when taxes were due. Cutting the percentage of silver in the coin was also a common trick. (Oddly, the gold coins used to pay soldiers retained their purity). The later coins, like we’re discussing weren’t really meant to deceive, everyone knew by that time that they were dealing with fiat currency.