Ron -

Here is a 7" sheath from a WWII Hunter with wide throat and small rivets. My Commando from 1944 has wide throat and large rivets. Both sheaths are basically identical save for the size of the rivets.

Note the "true" 3 1/2 grind as you described above with the upswept tip. The early post war models while not appearing to being fully two separate models, 3 and 4, it seems the grind was modified for the most part and they were on the way to that end without the exaggerated upswept tip as shown in the photo.

I don't think Mitchell's blade forging is a that early. I think it was forged closer to when it was assembled. As you know better than most, fighter production was nil in those days, so the majority of production was devoted to field knives. I could be wrong but it would seem unlikely (not impossible) that that knife was sitting around for 3 years or so prior to assembly.