Year 20 of Antoninus Pius's reign, which is what the "L K" regnal dating indicates — Alexandria's mint marked each year of an emperor's rule rather than using consular dating, a Ptolemaic administrative habit that Roman Egypt never abandoned. This was deep into one of the most administratively stable periods the province ever experienced, yet the billon tetradrachm coinage of Alexandria was already on its long slide in silver content, a debasement that would accelerate sharply under his successors.
Year 20 of Antoninus Pius's reign, which is what the "L K" regnal dating indicates — Alexandria's mint marked each year of an emperor's rule rather than using consular dating, a Ptolemaic administrative habit that Roman Egypt never abandoned. This was deep into one of the most administratively stable periods the province ever experienced, yet the billon tetradrachm coinage of Alexandria was already on its long slide in silver content, a debasement that would accelerate sharply under his successors.