AR24 - Antoninus Pius L ΙΘ

Year 19 of Antoninus Pius's reign corresponds to 155–156 AD, and Alexandrian billon tetradrachms of this period reflect the slow but measurable debasement of Egypt's distinctive closed currency system. The province was monetarily isolated from the rest of the empire — Roman silver could not circulate there, and Egyptian coinage could not leave. This arrangement, inherited from the Ptolemies and maintained by Rome, kept the imperial treasury's debasement invisible to provincial eyes.

By regnal year 19, the billon alloy had already shed much of its silver content from earlier Julio-Claudian levels. Dattari's original Cairo collection, from which many of these reference numbers derive, remains the type corpus against which most Alexandrian tetradrachms are still measured.