This set is in a wood and steel box made to be mounted on a wall. The upper panel slides off to remove the contents which include a 4mm sub-caliber barrel, a reloadable cartridge, a box of ammo and cleaning tools. The 4mm barrel has multi-grooved rifling. The reloadable steel cartridge unit is adjustable for headspace by screwing the base in or out. The front of the cartridge comes off to load a primer for propulsion. A 4mm lead ball is then loaded into the front of the cartridge. The paper and cardboard box of ammo has a partition to separate the lead shot from the primers.
The wood and steel box also serves as a target holder. The lower front panel has a wire sticking out of the front. Pulling a string attached to the wire causes a human shaped target to turn so that it can be shot at. I suppose a partner would pull the string and then release it after a few seconds so that the shooter could practice snap shooting. In addition to the small human targets there is also an assortment of stationary targets in various sizes. Inside the wooden box is a steel plate to stop the 4mm projectiles. The box also contains some literature including instructions. The instructions are for both the rifle and the .30 cal. Swiss Luger, but this set is only for the rifle. The rifle pictured appears to be the 7.5 K31.
Any information regarding this set would be of interest.