Antoninianus - Postumus MERCVRIO FELICI

Postumus founded the breakaway Gallic Empire in 260 AD after capturing and almost certainly executing Saloninus, the young son of Gallienus, at Cologne. He ruled for nearly a decade without ever marching on Rome — an unusual restraint that has puzzled historians. His mint output was prodigious and relatively well-organized, maintaining silver content in his billon issues at levels that outperformed contemporary Roman imperial coinage, which likely sustained confidence in his regime across Gaul, Britain, and Spain.

RIC V.1 #313 is a reasonably well-attested type from his middle period, well before his assassination by his own troops in 269 following his refusal to allow the sack of Mainz.