Constantine the Great Chi-Rho

[Gundobad]

Can you verify that this is a coin of Constantine the Great. The obverse legend shows (CONSTANTINUSMAXAVG) The reverse has two soldiers with one standard. The chi-rho is in the shield of the standard. The mint mark as I see it is  PLG. It appears the legend is the (GLORIA EXERCITUS).   

[Victor]

Your coin is his son -- Constantine II (RIC VIII Lyons 6)