AR21 - Diocletian L Α

Year One of Diocletian's reign in Egypt — marked by the regnal letter Α — falls in 285–286 CE, before his sweeping monetary reforms had taken hold. The Alexandrian mint was still operating under the old Ptolemaic-derived tetradrachm tradition, now heavily debased, a system that had persisted in Egypt largely in isolation from the rest of the Roman monetary world. Egypt functioned as a closed currency zone; coins from elsewhere in the empire did not circulate there, and these billon tetradrachms did not circulate outside it.

Diocletian would eventually shut down the Alexandria mint's distinctive local coinage entirely with his currency reform of 296–297 CE, ending nearly three centuries of uninterrupted provincial issue.