Postumus, 260-269. 23 mm. 3.38 grams.
IMP C POSTVMVS PF AVG
SALVS PROVINCIARVM, horned river-god reclining with left arm on urn and right arm on ship, prow to left

Sear III 10991. RIC 87.  Struck 260.

This early portrait looks a lot like Gallienus. Postumus revolted and became the "Gallo-Roman" emperor with his region bounded by the river Rhine, of which this is a personification.