Helena AE Follis, Antioch. 328-329 AD. 

Obv: FL HELENA-AVGVSTA, mantled bust right with necklace, wearing ladder 
 shaped diadem 
Rev: SECVRITAS-REIPVBLICE, Securitas standing left, lowering branch with left 
 hand, raising robe with right hand; right field

Mintmark dot SMANTB. 

RIC VII Antioch 82, rated R2.