POSTUMUS, Gallic Empire
AD 260-269
Billon Antoninianus. 3.47g, 21.7mm
MINTED: Trier mint, AD 266
REF: RIC V 60; Mairat 108-111
OBVERSE: IMP C POSTVMVS P F AVG, radiate, draped, and cuirassed bust right.
REVERSE: FORTVNA AVG, Fortuna standing left, holding rudder and cornucopia.

Notes:
Nicely toned, with a scattering of hard green malachite deposits on surface.  Traces of undertype or die clash on reverse. 
It's interesting that despite the fact Postumus was a usurper, his coins such as this one were generally better produced and of better metal quality than that of Gallienus, the legitimate emperor at the time.  
 
Provenance:
Ex E.E. Clain-Stefanelli Collection
Elvira Eliza Clain-Stefanelli (1914-2001) was born in Romania, and during World War II, she and her husband Vladimir were sent by the Gestapo to Buchenwald concentration camp. They survived their 3-year imprisonment and when the war was over, moved to Italy, where they worked in the numismatic trade. In 1951, they moved to the United States, where their knowledge and passion for numismatics led to them becoming curators of National Numismatics Collection at the Smithsonian. Together, they were also authors of numerous important reference works and curated an excellent personal collection of coins.
 
Historical Notes:
Postumus was one of the most successful of the 3rd century usurpers, establishing the break-away Gallic Empire.  He was the imperial legate of Lower Germany under Emperor Valerian, and when the latter was defeated and captured by the Persians, Postumus's troops proclaimed him Augustus against Valerian's son and co-ruler, Gallienus.  Gallienus's repeated attempts to crush Postumus's revolt never succeeded, and from 260 to 269, Postumus ruled over Gaul, Germany, Raetia, Britannia and Hispania.  Interestingly, the coins he struck were often of higher quality and better style than those of Gallienus.