AR22 - Gallienus (sole reign) (L ΙΕ)

By the time this tetradrachm was struck in regnal year 15, Gallienus had weathered more than a decade of near-continuous catastrophe — the capture of his father Valerian by Shapur I in 260, the breakaway Gallic Empire in the west, the Palmyrene expansion under Odaenathus in the east. Alexandria remained one of the few major mints still producing in his name. The billon content by this period had degraded sharply from earlier imperial standards, a reflection of chronic metal shortages rather than any local policy.