Here is a model 4-7 that I am told is from 1945. And probably just like you, I noticed the strange keeper strap on the sheath. I have also been told that the strap was made for a very short period of time by the Edward Bohlin Company, who made very fancy saddles and western gear at that time. I have seen one other strap/sheath like this on e-Bay. Has anyone here ever seen a strap like this? Any thoughts or comments are appreciated.