AR19 - Diocletian ΠΕΡΙΟΔΟϹ ΔΕΚΑΤΗ

This tetradrachm belongs to the final regnal year of Diocletian's coinage at Alexandria before his currency reform of 294 AD fundamentally dismantled the Egyptian monetary system. For nearly three centuries, Alexandria had operated a closed currency zone — provincial tetradrachms could not legally circulate outside Egypt, and foreign coins could not circulate within it. Diocletian ended this by integrating Egypt into the imperial coinage system, replacing the billon tetradrachm with the new argenteus and follis denominations. The ΠΕΡΙΟΔΟϹ ΔΕΚΑΤΗ legend marks this as Year Ten of Diocletian's reign — the last such dating the Alexandria mint would ever strike.