Aureus - Postumus Colonia

Postumus seized power in 260 AD following the capture of Emperor Valerian by the Sassanid Persians — a catastrophic humiliation that left the western provinces effectively ungoverned. He killed Gallienus's son Saloninus at Cologne and ruled his breakaway state for nearly a decade, maintaining Roman administrative forms with enough competence that many provincials preferred him to the legitimate court at Mediolanum. The Colonia mint — almost certainly Cologne — was his primary production center throughout his reign.

Elmer 135 is a relatively early type, placing it close to the foundation of the regime.