Gallic Empire or Gallic Roman Empire are names used in modern historiography for a breakaway Western European part of the Roman Empire that functioned de facto as a separate state from 260 to 274. It
Coin of Tetricus, last emperor (271–274) of the Gallic Empire
Marcus Cassianius Latinius Postumus was a Roman commander of Batavian origin, who ruled as emperor of the splinter state of the Roman Empire known to modern historians as the Gallic Empire. The Roman
Gallic Empire
…provinces without attempting to conquer Italy or otherwise seize the central Roman administrative apparatus. The Gallic Empire was established by Postumus in 260 in the wake of barbarian invasions and instability in Rome, and at its height included the territories of Germania, Gaul, Britannia, and Hispania…
Antoninianus of Postumus: IMP. C. POSTVMVS P. F. AVG
Milestone of Postumus c.261-269 found in Vitoria-Gasteiz, Spain. It bears the inscription: [I]MP(ERATORI) CAE[S(ARI)] [M]ARCO CA[SSIJANO] LAT[IN]IO POSTUMO AUG(USTO).
An antoninianus of Postumus. Legend: IMP. C. POSTVMVS P. F. AVG.
Antoninianus struck under Aureolus; Mediolanum (Milan) mint, AD 268. Left: Radiate, draped, and cuirassed bust Right: Hercules standing right, holding lion skin and club resting on rock