The source of the walnut is much less an issue than the relatively small surface area of the wood at the head of the stock, a design deficiency which appears to have been address in the 30s
A pre-1913 Regular frame stock; oil soaked and cracked
1936 Reg. frame; clearly more wood
1921 16g FW frame
1946 FW 16g
None of us can know what abuse a gun has experience in 75 years, and the head of the stock of your 12 should be examined. If no cracks, I would still consider cyanoacrylate impregnation of the wood.