The pistol is, I think, a Spanish 'Ruby' type made for the French army under contract during WW1. Note the French word 'Feu' for fire next to the safety catch. These were issued to a lot of second line troops like clerks etc. but were also issued to stretcher bearers, tank crews and Mortar teams. I believe that they were manufactured between 1914 - 1921, but perhaps Bill Grist can give you more accurate info as I'm not 100% on this.