A couple of things come to mind here Ron. The leather on the unmarked sheath, particulalry the nape on the rear, is a bit different than on the RMK marked sheath, although it is not atypical of Johnson leather. It does not appear to be Heiser leather nor stitiching for that matter.

Also, the keeper snap location is different than on the Johnson. If you look at Heiser or Johnson brown button sheaths from the period, generally the keeper snap is located in the middle of the sheath as on the example pictured, not to the far side as on the unmarked sheath. The Heiser is odd in that it has the keeper in that same location as the unmarked sheath. I can see that throwing you a curve ball.

One thing that really stands out is the guy that stiched it must have been have way though his bottle of Beam when he made this sheath. This, is reminicent of Stockman quality, or lack thereof.

I don't think it is unreasonable to say this could be an early Johnson prototype or 'one off' not unlike Stockman had been doing for some time. Based on the evidence we have seen over the years, I think it stands to reason and the concensus seems to be Maurice Johnson was involved at some level as early as 1960, but definitely by 1961.

You do have to consider that this whole thing could be explained away by an interupption of the supply of or running short of the logo marked brown buttons.