This is an apparent bring-back Belgian Model 1935 Mauser with an un-repaired 'duffle cut' just forward of the rear barrel band. As most know or can find after a simple search, these were Belgium's interwar rifle design, differing from the popular Model 1924 designs being built at FN for foreign contracts. Unlike many of her foreign clients, Belgium opted to stay with the 7.65x53mm chambering for her rifles, continuing on from the Model 1889 design. The Model 1935 was chambered in the same caliber as was the 'updated' version of the Model 1889, the Model 1889/36.
This one is a bolt-only mismatch, with apparently original stamped numbers on the receiver, barrel, trigger guard, floor plate, stock and butt plate. Like other rifles built at Manufacture D'Armes De L'Etat (MAE), this rifle used salvaged components from German Gewehr 98 rifles, most noticeably on the cross bolt, magazine floor plate and action screws. Instead of a wooden plaque insert with stamped stock numbers, this one had the numbers stamped directly into the stock. The stock itself has a nice MAE cartouche on the right side. There are also three other stamps in the stock. Forward of the trigger guard there is what appears to be a circled 'A' in script indicating 'finished wood.' Behind the trigger guard is a small circled 'H,' an intermediate Belgian control marking. On the keel of the stock between the rear sling swivel and the butt plate is a small eight-pointed star or sunburst design of some sort. The latter appears less refined in design and a bit more crude. The stock was likely manufactured at the time of the build as there are no signs at all of having been salvaged from another rifle.
The bolt is a mystery to me. I posted pics of it before on other fora, and a few people believe it was/is Turkish. I lack enough experience with Turkish arms to say one way or the other. There are a number of odd shapes stamped into the bolt components that I haven't seen represented on the few Turkish or Turkish-contract rifles I've owned/examined before. All of the bolt components are stamped matching. I guess the easy way out is to say that this bolt was mated to this rifle after arrival in the US, but the bluing of the bolt strongly suggests WWII German depot treatment. I've seen the same quality, tone and wear coloring of the bluing on German-capture weapons of foreign origin and manufacture that I own. My best guess is that if it is indeed Turkish, it may be from a salvaged Turkish reparation rifle cannibalized by the Belgians like the many German Gewehr 98s that came into their possession following the end of WWI. The Belgian use of some Turkish arms is already established, so the use of some usable components would not have been unlikely. It is probable that this same bolt was blued by the Germans for use with this rifle to replace the bolt it had prior to being captured.