As said above, it's a French service pistol, modele 1935S, from the mid 30s. They only made 1404 before WW II started, and the Germans didn't put it into production, as they did with the 35A. After the war, production started in earnest, and it stayed in use even after the adoption of the Modele 1050 in 9mm P. The production history is quite convoluted. Although blocky looking, the pistolt fits the hand well and has big sights for rapid sight acquisiton. The majority of them were Parkerized, but during the late 40s, when the demand was greatest, some were blued. Some were also black enameled, like the 1935As. The M1 in the markings means that the safety was modified to move in the same diretion as that of the 1935A, for uniformity and ease in training.
Gend Medlin and I wrote the book on them: The French 1935 Pistols, which is still available, I think, from some gun book sellers. We only had 1000 copies printed, and that they're still available says something about the popularity of French weapons.
7.65 French Long ammo is a real problem. You can make it by turning the rim off 32 S&W Long, cutting an extraction groove, and shortening it, but a lathe is required. Quite a few dealers in weird ammo have it in stock.
Here's the only picture I have of them. the 35A is on top, with an HSc in the middle and a 35S on the bottom.