https://www.moderncoinmart.com/info-vault/articles/the-roman-silver-denarius.html
Debasement affected the Silver denarius throughout the years. Small amounts of copper were added to the silver, and the weight of the coin was decreased. 141 BC, the Roman denarius weighed 1/84th of a Roman pound (3.9g).
It is an old trick. Make sure to get the denarius that was coined when the Romans started their monetary system, and make sure to “...render unto God, what is God’s.
Are you talking about seigniorage?