Diocletian, 284-305, Antoninianus

Diocletian, antoninianus, billon, reign AD 284–305, Antioch mint, struck c. AD 285–286, 3.3 g, 22 mm. Obverse with radiate, draped and cuirassed bust right, legend MP C C VAL DIOCLETIANVS P F AVG. Reverse CONCORDIA MILITVM, Concordia standing left, holding standard and scepter; in exergue XXI, with officina mark Z in field. Well-centered strike with clear legends and principal devices; typical billon fabric for the early Tetrarchic reform period. RIC V Diocletian 322.

The type belongs to the early issues of Diocletian, produced during the consolidation of power after the Crisis of the Third Century, and employs the reverse legend CONCORDIA MILITVM to emphasize unity between the emperor and the army, a central requirement for stability during his initial campaigns and administrative reorganization that culminated in the Tetrarchic system. The XXI mark reflects contemporary tariffing or alloy-control conventions used on antoniniani in this period.