Gallienus Antoninianus. Rome mint.

Obv: GALLIENVS AVG, radiate head right
Rev: MARTI PACIFERO, Mars standing (or walking) left, holding
olive branch, spear and shield
Left field: A

RIC V-1 (Sole reign), Rome 236, rated common

With permission of Roma Numismatics, October, 2009

Note the formation of the letter M, written IIII of the
word "MARTI". This type of M is a unique characteristic of
coins from the Rome mint (on coins of Claudius II too). dk