Sorting through French family pictures, papers and glass slides. Trying to put names to faces.
The picture below is the same gentleman (on the right) with his brother, who he had just bumped in to on the front.
It would take a better scan to be 100% certain, but it looks like an Adrian helmet, with crossed cannons indicating an artillery unit.
Branch insignia in the form of a grenade for line infantry and cavalry, a bugle horn for chasseurs, crossed cannon for artillery, an anchor for colonial troops and a crescent for North African units was attached to the front.
A nice example can be seen at the Australian War Memorial:
So yes, French, WW1 era, after 1915.