my guess is a WWII knife, made local for a departing GI or a theater made knife by a rear echelon shop, based on the immensely popular Marbles Ideal. The knife seems to predate the Jet Pilot knife given that owner died in the 1950s when the 6" Jet Pilot a very new thing and hardly in need of a rehandle. The Mk2 and Jet pilot both based on the Ideal pattern. Whether an original blade or rework of existing blade might be observed by ricasso symmetry or any sign an original mark ground away and replaced by Mr Most's stamp.