On the death of Decius in AD 251, Trebonianus Gallus, governor of Moesia, was hailed emperor by his troops. He appointed Hostilian as Augustus and Volusian, his own son, as Caesar. When Hostilian died of the plague, Volusian was raised to the rank of Augustus and became co-emperor. Their brief reign ended in AD 253 at Interamna, when both Trebonianus and Volusian were defeated and slain.
Early antoniniani of Gallus and Volusian initially distinguish reverses of Felicitas Publica, Pietas, Libertas (for Gallus), sometimes showing a star in the reverse field, and for Volusian the reverse types of Virtus, Pax and Concordia. The obverse legend for Gallus usually reads IMP C C VIB TREB GALLVS AVG. The antoninianus above differs slightly from the Rome series by the use of a different obverse legend and probably came from the mint Viminacium in Moesia.

Obv. Trebonianus Gallus, radiate facing right, draped, cuirassed, IMP CAE C VIB TREB GALLVS AVG.
Rev. Libertas standing left, holding a pileus and a sceptre, a star in the reverse field, LIBERTAS AVGG.