AR24 - Marcus Aurelius L Δ

Year 4 of the joint reign of Marcus Aurelius and Lucius Verus — the only time Rome had two equal co-emperors simultaneously — fell precisely during the Parthian War, when Verus was nominally commanding Roman forces in the East while Aurelius managed affairs in Rome. The Alexandrian mint was unusually active in this period, supplying the monetized economy of Roman Egypt, which operated in deliberate isolation from the imperial silver coinage through its closed currency system.

Emmett records this as a fourth-year issue, placing it securely in 163/164 AD by the Egyptian regnal calendar.