[Dan in Wichita]

When the U.S. minted silver coins for regular circulation (1794-1964), they contained about 10 copper as well. The copper was mixed in with the silver because it made the coin more durable and suitable for circulation. Silver by itself is very soft. Same is true for gold coins.

Perhaps the Romans discovered the benefit of alloying silver with a bit of copper.

[SunkenCiv]

Thanks Dan!

[Adder]

Perhaps the Romans discovered the benefit of alloying silver with a bit of copper.

True, I am sure.

But the Romans cut the content of the precious metals as the economic times/greed* required, so the amount of silver in this case would fluctuate. This happened numerous times in the republic and later, the empire. By the time of Caracalla, the silver in a denarius was something like 5%.
* Emperors were fond of cutting the silver content so they could pay for lavish spending and paying off the Praetorians and army. More coins at the same value for less actual silver.

[AlmaKing]

That’s correct in my opinion.

10% copper is not debasement. It is for strength and durability.

We do this in other industries as well such as semiconductors and steel. Alloys have always been used to improve characteristics of the pure metal whether its iron, silicon, aluminum, silver, and even gold.