267-268 AD., Aureolus in the name of Postumus, Antoninianus, mint of Mediolanum, RIC 378.

Aureolus in the name of Postumus, Antoninianus, 19 mm, 2,05 g., mint of Mediolanum (Milan), first officina, 267-268 AD.
Obv.: IMP POSTVMVS AV[G] , radiate, draped and cuirassed bust right.
Rev.: FIDE[S EQVI]T / P , Fides seated left, holding patera and military standard.
RIC 378 ; C 60 ; Elmer 612 ; AGK 18 c .

For the time Gallienus campaigned against the Goths in eastern Europe in 268 AD he had placed Aureolus in command of the legions in northern Italy to protect Rome from invasion by Postumus.
When the emperor was conducting his eastern campaign, Aureolus openly declared for Postumus, and issued a series of coinage in the name of Postumus from Mediolanum. It is uncertain what Postumus's attitude was towards this event, but he obviously was unable to commit any forces (due to Laelianus's uprising) to help Aureolus, who was soon beseiged in Mediolanum by Gallienus.
Nonetheless, during the siege Gallienus was assassinated, and was replaced by Claudius II.
Upon hearing of this event, Aureolus attempted to make peace, but Claudius refused, which forced Aureolus to capitulate, hoping for leniency. In this time of constant upheaval, there could be no room for Claudius to be lenient, and Aureolus was put to death.