The general thought behind the portrait is that it is a depiction of Saint Maurice, given that he is named on the coins (S.M. Vienne). However given the variations in the portraiture I have some doubts concerning that. Sometimes you will find these coins with `St Maurice' sporting a beard, sometimes clean shaven. Sometimes supporting a mullet, and sometimes a little more conservative hairstyle.
The reverse of this one sports a short cross with four pellets. It is very similar to Roberts 5046, but not quite. The legend reads MAXIMA GALL.