Joe,
I've got several 40's/ early 50's model 3's & 4's and every single one has the same finger grips as that knife. Not a coincidence, had to be the same guy grinding them, but who (Bill Platts)? They are all deeply cut and retain just a hint of the outer bark in-between.
Great knife and thanks for sharing.
Probably not at that time would be my guess. Being foreman, I don't know how much actual knife making he was doing versus management. Scott might have a better handle on that if the shop is run in somewhat the same manner as it was when Bill Platts was foreman.
Looking back into the 40's, the style of finger grips was deep with bark between, not to a point or "softer" transition, but real separation. Seems that style held up to some degree into the 50's.