Constantine II AE follis. Siscia. AD 320. 18mm, 2.14 g. 

CONSTANTINVS IVN NOB C, laureate, draped and cuirassed bust 
left, holding Victory on globe and mappa.
VIRTVS EXERCIT, Standard inscribed VOT XX in two lines with 
two captives sitting at its base.

Star (or rudimentary chi-rho) in left field.
Mintmark Epsilon SIS star.

Bikic-Do hoard 756 var (officina); RIC VII Siscia 138-139 
var (emperor)
Very rare. 

With permission of cngcoins.com, Feb 2016
Auction 368, Lot 496, Feb 2016
Estimate $150.