A quite interesting found. Plate holder for 12 (twelve!) plates made of ebony wood and aluminum. A roller blind pushes the exposed plate into the leather bag. Then it needs some practice to find the plate in the leather bag and put it between thumb and forefinger in the upper position above the other plates. A mechanical counter completes the holder. To change from sheaths to glass plates there is a build in mechanism to widen the slit between roller dark slide and mechanism permitting the sheath or glass plate access to the leather changing back.
Photos © Jo Lommen