Here is an interesting observation about very early WWII. Both Compton's knife and Erroll Flynn's knife have a relatively wide, thin, flat strip of leather used for the wrist thong... not at all similar to later cord-like leather thongs. Just thought I would point that out...
Also, here are a couple of older WWII example sheaths just for grins... The top blade (SS sheath?) reminds me a little of the profile of Col. Compton's knife.