Æ18 - Antoninus Pius L ΚΔ

Year 24 of Antoninus Pius's reign, which is what the ΚΔ regnal date records — a Alexandrian convention that allows precise annual attribution in a reign otherwise difficult to sequence. The Alexandrian mint operated under Roman prefectural authority and maintained its own dating system tied to the Egyptian calendar year beginning in late August, meaning this piece was struck in the twelve-month window between 29 August 160 and 28 August 161.