289-290 AD, Diocletian, Siscia mint, AE-Antoninianus, RIC 264.

Diocletian, silvered AE-Antoninianus (pre-reform), 3.11g., 23mm, mint of Siscia 1st officina, 289-290 AD
Obv.: IMP C C VAL DIOCLETIANVS P AVG , Radiate and cuirassed bust right
Rev.: CONSERVATOR AVGG , Jupiter on the right standing left and Diocletian on the left standng right (facing each other), each sacrificing from patera, over a tripod type alter; with A in left field, in ex.: "dot" XXI "dot" I "dot"
RIC V Part II, p. 247, # 264 ; C 44