Constantine I, AE follis, Siscia. 

CONSTAN-TINVS AVG, helmeted, cuirassed bust right.
VICT dot LAETAE PRINC PERP, two Victories standing facing 
each other, holding shield inscribed VOT PR on an altar 
decorated with the letter S (Helvetica 6f). 

Mintmark Epsilon SIS dot. 

RIC VII 102 var (obv. legend for this mintmark).