AR23 - Antoninus Pius L Κ

Year 20 of Antoninus Pius's reign — the regnal year encoded in the "L Κ" notation — fell during one of the more administratively stable periods of Roman Egypt, when the Alexandrian mint was producing billon tetradrachms at a pace reflecting both population demand and the prefecture's relative prosperity. The billon alloy used at Alexandria was already debased well below early imperial standards by this point, a slow degradation that had been underway since Nero's currency reforms of 64 AD fundamentally altered Egyptian monetary practice.