It's a very cool little pistol. I bet there's not too many of them around!I have an early 20's model German made Lignose Einhand.
It its a semi auto and is cocked by putting a finger in the front of the trigger guard to cycle the action.
The pistol was developed as a self defense pistol in .25 auto for soldiers after WWI that had lost an arm or hand.
Later in WWII it was issued to German General officers to be put into a holster in their hats to be used as a last chance weapon or for suicide prior to capture.
Drury has shot it. At 15 yards he hit a 3" swinger more than once.