First off, its not GLORIA EXERCITVS (Glory of the army - soldiers with standard(s)) - it is the much nicer and rarer VIRTVS EXERCIT (Virtue of the army - standard with seated captive barbarians either side). Minted london mint (mint mark PLON).
However, there is no issue with the same legend breaks. Even Helvetica fails to list this legend break. Tesorillo lists this legend break but does not couple it to this bust.
Helvetica is pretty extensive, so this is probably a new variety.
So:
Constantine II, 320-321 AD
CONSTANT-INVS IVN NC - Radiate, Draped, Cuirassed bust left
VIRTVS EXERCIT - Standard with VOT/XX on banner, captive seated either side
PLON - London Mint
Perty cool. Heres on of the same legend break on Vcoins, listed as though there is no
break:
http://www.vcoins.com/en/stores/cyb...Default.aspx