Silver antoninianus, 22mm, 3.28gm, issued AD 260-265 Cologne mint.
Obv: IMP C POSTVMVS PF AVG, Radiate, draped and cuirassed bust facing right.
Rev: HERC DEVSONIENSI, Hercules standing right resting on club and holding bow, lion skin over arm.
References: Sear 10944, RIC 64, RSC 91.
Reverse refers to the cult of Hercules at Deuso (modern Deutz), across the river from Cologne.