Index of Papyri
Ancient coins mentioned in the Robert C. Horn Papyri Collection include the solidus and the drachma.
The drachma was an adaption of Greek coinage in Roman Egypt. Most of the coins used were struck in the Alexandrian mint. Fundamentally one (gold) bullion tetradrachma equaled six bronze drachmas, equaled 12 bronze diobols, equaled 24 bronze obols.
The solidus replaced the older Roman aureus in 312 AD by decree of Emperor Constantine. It was a gold coin which maintained its value over time; when taken in by the imperial treasury (taxes had to be paid in solidi), it was re-minted, which assured uniform weight. Thus it became a desirable coin for trade even beyond the bounds of the Empire (although legally such usage was forbidden).