AR24 - Commodus L ΚΑ

Year 21 of Commodus — regnal year ΚΑ — falls in 180-181 AD, the first full year of his sole reign following the death of Marcus Aurelius in March 180. The Alexandrian mint, operating under Roman provincial authority, dated coins by regnal year rather than consular year, making Egyptian billon tetradrachms an unusually precise chronological tool for historians tracking the transition between reigns.

Commodus would rule for another eleven years before his assassination on New Year's Eve 192 AD. The Dattari reference here draws on Giovanni Dattari's landmark 1901 corpus compiled almost entirely from coins excavated in Egypt.