Rome, Ca. AD 241-243
Gordian III Av. aureus, Rome. IMP GORDIANVS PIVS FEL AVG; laureate, draped and cuirassed bust right. Rev. SECVRITAS PVBLICA; Securitas seated left, holding sceptre and resting head on left hand. RIC IV-3 124; Cohen 339; Munich 184299.
 
Gordian III was proclaimed Caesar by the joint emperors Balbinus and Pupienus, rising quickly to the rank of Augustus following their murder through the support of the Praetorian guard. Ascending to the throne at 13 years old, Gordion III was the youngest Roman emperor to rule alone, a fact reflected in his clean-shaven appearance on this aureus. 
 
He is also depicted cuirassed on the obverse, innkeeping with nearly all imperial coin portraiture of the 3rd century AD. This choice was perhaps in response to the military anarchy of the time but is 
underscored by Gordion III’s successful military campaigns, driving the Persians out of Mesopotamia in AD 242. Following this campaign, his coin portraits feature a bearded portrait.

For additional information see: 
Sear, D. R., 1988, Roman Coins and Their Values Volume 1: The Republic and the Twelve Caesars, 280 BC - AD 96. London.