Which War?
FN-49. Starting date?Apart from Pre-ww2 prototypes and wartime fiddling in Britain, not much happened until 1946), after the Germans had long gone and FN were rising from the seriously battered ashes..
I doubt Egypt would have done a 7mm conversions it is fairly certain they never used the cartridge anywhere else. Until Nasser linked up with the soviets in the mid 1950s, 7.92 x 57 was THE service cartridge in Egypt. Note also the Egyptian 7.92 x 57 version of the SwedishAG-42, from which they developed the very cute 7.62 x 39 "Rashid". carbine.
Venezuela was one of the few customers for 7 x 57. They liked 7mm so much that their initial FAL purchase was in 7mm "Liviano"; basically 7.62 NATO necked down to 7mm. Apparently also known as the "7mm, second optimum"; developed during the last gasps of the EM2. This cartridge later resurfaced as a "legitemized" sporting wildcat, the 7mm-08.
Buy the rifle, not the story. The early and late "trials" SAFN / FN-49 models are VERY collectible, but most are in "official" museums. Does this one come with an "original hooked-quillon" bayonet?