AR23 - Severus Alexander L ΙΒ

Year 12 of Severus Alexander's reign coincided with a period of mounting military pressure on Rome's eastern frontier, where the newly resurgent Sasanian Empire under Ardashir I had begun pushing aggressively into Roman Mesopotamia. Alexandria's imperial mint continued producing its distinctive billon tetradrachms throughout, the Egyptian monetary system remaining deliberately isolated from the Roman denarius economy — a policy in place since Augustus closed the province to outside coinage.

Billon content in Alexandrian tetradrachms had been degrading steadily through the Severan dynasty, and by regnal year 12 the silver fraction was a fraction of what Nero's reform issues had carried a century and a half earlier.