Jack,
I spoke with Gary quite recently. His wording was not mis-heard. He stated that he "knew" his Father was "actively" seeking other sheath makers. Samples were received from a few and, even the "Heiser former employee", with no records had "sample" examples? Jack: We can all speculate and..hell I have no certainty about this era. I was younger than Gary.
GTR also has no recall of the name of the harness maker who has been tied to some of this mystery. Does that make it not so? Perhaps. I would wonder why Heiser would send "samples" to the Randall shop, after already having been making these sheaths for decades, especially when Bo Randall was actively trying to find somebody else?
I love the pashion you pursue these questions with Jack. I hope you, (we) whomever can get a finite answer someday. Maybe this is just what makes this "Randall thing" so much darn fun! Keep up the good hunt, Jack. I am not one to jump in on posts and expound kudos, be it new knives or research on "oldies", but I appreciate you dedicating your time in the strife.
Best, Capt. Chris