I think you are talking about the model 3 sheaths Ron posted.
The keeper snap placement "thesis" put out by Jack I think at this time is proven invalid. It is evident that Johnson made center snap sheaths, again shown in Jimmy's photo above, and he moved it over. We know that.
I originally was asking about the four model 1 sheaths posted on page four of this thread. In any event, you are looking at these things now.
Ronnie -
The button issue is as I think was stated simply different dye lots. With some researsch, I suppose one could make a case, but I don't think it will be necessary. There is plenty of other things to looks at.