For this issue from Ostia, there is a variation mention in RIC. The most common type is the first coin below; which only has a flag on the center standard, with the eagle. The second coin, which is the scarcer variation, also has a flag on the vexillum topped with a hand.
Constantine I
A.D. 312-313
IMP C CONSTANTINVS P F AVG; laureate and cuirassed bust right.
SPQR OPTIMO PRINCIPI; Legionary eagle (to the left) between two vexilla, that on left surmounted by a right hand, that on right by a wreath; flag on the eagle and sometimes left vexillum.
in ex MOST[P]
RIC VI Ostia 94