Very rare type of weapon

This buckle pistol, created in the 30s of the last century in Nazi Germany.
Since the scope of use buckle pistol was very limited, they were released quite a bit.
Running the whole thing is very simple.
There are two types of buckles, guns - and dvuhstvolny chetyrehstvolnaya (7, 65 and 5, respectively, 6-gauge).
By pressing the button, the top of the buckle opens and immediately be shot.
In other models, after opening the buckle must still pull the trigger.