Severus Alexander. 222 - 235 AD. AR denarius. Rome mint, struck 231-235 AD. 

IMP ALEXANDER PIVS AVG, laureate, draped and cuirassed bust right. 
MARS VLTOR, Mars, helmeted, walking right, holding spear and shield. 

RIC 246; RSC 161; BMCRE 834-836; Sear 7882.