Constantine I. AE Follis. Siscia. 320 AD. 

CONS-TANTINVS AVG, helmeted, cuirassed bust right.
VIRTVS-EXERCIT, two captives seated at the base of a standard inscribed VOT XX. 
S-F over HL across fields. 
Mintmark Delta SIS star. 

RIC VII Siscia 120. Very rare (R3).

With permission of Roma Numismatics, Jul, 2010