Hi JA,
I was surprised it was as clear too.
I "think" it is the Royal Irish Rifles too, but I'm no expert and I'm basing it on trying to zoom in a bit on badges and the fact that somebody told me most Belfast men were in the R.I.R. I only know his (my great grandfather's) name; birth/death dates; his wife's name and the handkerchief card (more basic version of yours) addressed to 30 Matlock St.
I do remember my granny (his daughter's) house in 14 Matlock street. I found the photos and handkerchiefs etc among her papers. There was another cloth handkerchief (not on card) which I'll post here, when I get an image. The only reason I'm presuming this photo might be France is because the card came from there too. There was a rumour he'd been injured/gassed but I have no proof of that. I know he died after the war.
Good time to remember them with the 100 anniversary coming up.
Noel