I'm no expert on this, but I was always under the impression for base metal imperial issues that they circulated until worn, after which they would be countermarked. Especially at the edges of the empire. Of course there are other reasons for counter marking.
That makes sense. I was thinking more about the denarius. Would an older silver slug have been worth as much as a newly minted denarius?
May I join the unanimous congratulations and thanks for sharing this fascinating information, particularly the coins found in the villa.
Fantastic ancient site Oplontis, one of the highlights of my 2019 trip to Southern Italy (lucky I didn't leave it later to go). In immaculate condition for it's age like Herculaneum well below street level as some of my pics show.