Along with the Sep Serverus I posted earlier, I purchased three other coins from the same dealer. This is the second of the four.
Elagabalus Denarius, RIC IV 107, struck at Rome, 220-21 AD:

OBV: IMP ANTONINVS PIVS AVG, laureate & draped bust right
REV: LIBERTAS AVG, Libertas standing left, holding pileus & scepter, star in left or right field
2.35g, 19mm