Double Sestertius - Postumus FIDES MILITVM, Lugdunum

Postumus founded the Gallic Empire in 260 AD after capturing — and almost certainly executing — Saloninus, the young co-emperor left in charge of the Rhine frontier by his father Gallienus. The double sestertius denomination itself was an innovation of the Gallic mint, effectively doubling the nominal value of a denomination already struggling against rampant debasement in the central empire. FIDES MILITVM was not decorative piety — Postumus held power for nine years entirely on the loyalty of Rhine legions who had proclaimed him in the first place, and that relationship required constant, explicit acknowledgment on the coinage.

He was ultimately killed in 269 by his own troops after refusing to allow the sack of Mainz.