AR23 - Antoninus Pius L ΙΘ

Year 19 of Antoninus Pius's reign, struck at the Alexandria mint under Roman provincial administration. Egypt operated its own closed currency system — Roman citizens arriving in the province were required to exchange their silver for local billon coinage, and Egyptian coins could not legally be exported. This monetary isolation kept the Alexandrian mint effectively independent in character long after Egypt itself was anything but.

The billon alloy had been deteriorating steadily since the early second century, and by this regnal year the silver content was a fraction of what Ptolemaic tetradrachms once carried.