WJS was an unknown inspector at Springfield in the 1918-1921 period. Supposedly, he also helped out at Rock Island for a limited period.
I agree about the comment that at least the stock was correct to the ship (A Brooklyn-class light cruiser which had a distinguished career in the Pacific from Pearl Harbor-on).
I would guess the stock (or rifle) came from the U.S. Navy detachment - the Marines could be moved from station to station and carried their rifles with them - thus, no need to mark the stocks.
I have seen several rifles with POD stocks (Philippine Ordnance Depot), but I never know if the whole rifle went through there or not.