Constans, AE medallion, Rome, 35 mm, AD 337-350. 

CONSTANS PF AVG, laurel and rosette-diademed, draped, cuirassed bust right.
VICTORIA AVGG NN, Victory sitting right on cuirass, inscribing VOT XX 
on a shield held on her knee.

Gnecchi 19; RIC 382; Cohen 130; BMC 7 (this coin).