Oh man...am I in trouble! The top holster construction expert has put me on the spot. Jerry, what got me started down this primrose path were the things you picked up on, the gauge of the material and the pebble finish. It just looks like the few paper holsters I have seen, but in magnificent condition. It obviously was not carried much and has been stored in the best of conditions. One of the things that did influence my thoughts is shown in the shot of the open holster with the Luger in it. If you look closely at the blown-up photo, you can see what appears to be a double layer of material on the top edge of the holster just to the right of the pull-up strap and on the leading edge of the magazine pouch.
I am not at all certain it is paper. It certainly does not exhibit any foxing or separation of the layers that you would expect. I guess it is either leather or an extremely rare mint ersatz holster.
