George’s safety depot box contained his journal and three coins, presumed by Rick to be Roman. That would be a fairly good guess. Roman coins were the standard currency in the Romanized portion of Britain from not long after the conquest, around A.D.43 (and they were already in common use long before that), until well into the Middle Ages.
The Romans established two mints in Britain during the late 3rd century. One had a mint mark including the letter L, almost certainly Londinium (London). The location of the other, which used the mint mark C or CL, is still in doubt. Camulodum (Colchester) or Clausentum (Bitterne, near Southampton) are leading contenders. Originally, three demoninations were struck: one each in gold, silver and silvered-bronze. A smaller bronze coin followed several years later.
The mysterious “C” mint did not stay in operation very long, but the London mint produced no less than 587 different combination of obverse and reverse types and mint marks up until A.D.325, after which it was closed. During the brief reign of Maximus (A.D. 383-388), the London mint was reopened, producing gold and silver coins with the mintmark AVG; all of which are extremely rare.
I was surprised to learn that forgery of Roman coins were common after the Romans left the British isles; apparently, the “barbarians” were relatively easy to fool.
Like all collectable coins, value is based on scarcity and condition. Ebay offers Roman coins from a high of $9400 to the omnipresent 99¢. The most expensive coin currently offered that was minted in London is a Constantine I coin marked 321AD, offered for $238 (shown below).