Gallienus, AE antoninianus. Rome. Sole reign. AD 263. 

GALLIENVS AVG, radiate, cuirassed bust right.
MARTI PACIFERO, Mars standing left, holding olive branch, spear 
and shield. 

A in left field. 

RIC V-1 Rome 236; Goebl 0569a; Sear 10288. 

Image from the Dalheim hoard catalog.