Back in the rivetd days, #18's, and #15's even had their own model stampings, even though (especially with a #15/ sawteeth) the blade shapes were almost identical. The old (first?) Heiser model "C" style sheaths from the 60's were so stamped. Some had, what I call, "canteen snaps". Pete (Hamilton) always called them "lift to dot" snaps. I cannot address when Johnson did and did not stamp the models, but that practice died quickly. Hope this helps.
Best, Capt. Chris
PS: I don't have a copy handy, but I am sure there are photos of this type of sheath in Pete's book. (unless I'm imagining it...totally possible)...CCS