The mask is Irish, which would mean that the emeralds were too. It's mentioned that the Romans broke several pieces up and reused them but the Romans never occupied Ireland and only controlled a small portion of England and Wales during the reign of the Emperor Claudius.
Veronica Kipling states that Claudius was the Emperor of Rome from 45 AD to 54 AD. In reality, his reign lasted from 41 AD to 54 AD.
At the auction Jimmy asks Lois for twenty dollars and she hands him a dollar bill.