Hello and welcome to the site.
First of all, there is a forum section for identification requests, this thread is on the free discussion section.
Secondly, we require basic measurements and better photos for filtering our search.
Diameter will suffice, and photos with the coin preferably out of the holder.
That said, I can already give you a direction without the informations above.
While the portrait at obverse is very worn, a part of the reverse is well visible.
Your coin is a Roman nummus from the Constantinian period, with the reverse showing a soldier striking a fallen warrior and the lettering FEL TEMP REPARATIO.