Could be Constans, could be Constantius - you might be able to tell in hand. The letters to the right of the emperors head will say '*VS PF AVG' if it is Constantius II, and '*NS PF AVG'. The bust shows the emperor holding a globe. The reverse is FEL TEMP REPARATIO (something along the lines of 'Happy times are back') and shows the emperor striding left over two captives, like this:
Hot linking to Wildwind images will not work.
With clear photographs, we could probably make out the mint mark and pin down the emperor a bit better. If you'd like to try that with it in hand, go to the Wildwinds page for Constans and try to match up the mintmark and legend to a listing and it will tell you the reference number.