AR23 - Marcus Aurelius L Δ

Year 4 of Marcus Aurelius's reign as sole emperor — the first year following Antoninus Pius's death in 161 — coincided almost exactly with the outbreak of the Parthian War, when Vologases IV seized Armenia and destroyed a Roman legion at Elegeia. Alexandria, as the administrative and monetary hub of Roman Egypt, continued issuing its distinctive billon tetradrachms under a closed currency system that prohibited imported coinage and forced all bullion into the provincial mint. The tetradrachm never circulated outside Egypt's borders.