Most 4th century Roman coins weren’t made from precious metals (with the exception of the gold used to pay the army). The article says these were copper and bronze. Smaller and thiner than a dime. The Romans did “wash” them in silver to make them look more valuable than they really were. Kind of like when the silver disappeared from US coins in 1965.
That’s true! I remember reading that this was happening in the late western period.
I guess the more things change ...