I'm curious as to the marking in the magazine cutoff notch. Replacement stocks made for USGI arsenals had an "S" (Springfield Armory) or "K" (Keystone) in the cutoff notch. I'd be surprised if FN actually made stocks, American Walnut being fairly difficult to get in Europe during WW2. FN had a huge contract to rebuild M1icon rifles in 1947-1949, but not 1903-type rifles.