RIC 726, Siscia. Bust type F. Denomination: Antoninianus.
Pink attributes this coin to the first emission of Rome.

OBV.: IMP C M AVR PROBVS AVG

Radiate, cuirassed bust right.

REV.: PROVIDENTIA AVG

Providentia standing left, holding baton and cornucopiae; at foot, globe.

Mintmark: / XXIA

Image provided courtesy of Plamen Arsoff, Ancient Treasures