Postumus AR denarius. AD 260-269. Cologne. 19 mm, 3.32 g. 

POSTVMVS PIVS FELIX AVG, jugate busts right of Postumus, laureate and cuirassed, and Hercules, laureate.
HERCVLI ARGIVO, Hercules standing left, wielding club at the hydra which has coiled tentacles around his waist and leg.

RIC V-II Cologne 341; Cohen 110; Berlin 18263036.

Image courtesy of the Münzkabinett Berlin.