The legend begins D N MAG which combined with the portrait style means it is Magnentius.
And a very nice Magnentius it is too ! Many of his coins are concidered 'unofficial' and have a low standard of quality.
This one seems to be quite reasonable although I cannot quite make out the mint mark on the bottom reverse side. LPAR perhaps ?
If so it is Arles which is good !
You did well with this one.