AR24 - Antoninus Pius L ΚΑ

Year 21 of Antoninus Pius's reign, rendered here as L ΚΑ in the Alexandrian regnal dating system. The Alexandria mint operated under Roman imperial authority but maintained its own distinct coinage tradition, producing billon tetradrachms that circulated exclusively within Egypt — a monetary quarantine enforced since Ptolemaic times and continued under Rome to control bullion flows in and out of the province. By this point in Antoninus Pius's reign, the billon alloy had degraded noticeably from Trajanic-era fineness, a deliberate policy rather than an accident of supply.