Helena, AV Solidus, Thessalonica. AD 318-319. 

FL HELENA AVGVSTA, diademed, mantled bust right, wearing 
double pearl necklace.
SECVRITAS REIPVBLICE, Securitas standing left, lowering branch
and raising hem of robe.

Mintmark SMTS. 

RIC VII Thessalonica 149; Sear 16587 var (mintmark). 

With permission of cngcoins.com, August 2003.