Constans, AE18, 2.20 gr. Lyons. Struck AD 342. 

CONSTANS PF AVG, laurel-and-rosette-diademed, draped and 
cuirassed bust right.
VICTORIA AVGVSTORV (sic), Victory walking left, holding 
wreath and palm branch.
Mintmark SLG. 

RIC VIII Lyons 37; Lyons 46; LRBC 255. 
Extremely rare. Only one other example cited in Lyons.

With permission of cngcoins.com, auction Sept. 2010, lot 1532. Est. $150.