Text copied from TM9-1985-2 German Explosive Ordnance 1953 :
"Safety fuze igniter (Percussion type)"
Igniter consists of a cylindrical brass body containing a spring loaded striker held in position by a friction fit of the Z type with a cap to which is attached a large steel ring.
The percussion cap holder is threaded outside throughout the entire length, thus allowing it to be screwed into the igniter in either a safe (percussion cap away from the striker) or armed (percussion cap toward the striker) position.
A strong pull on the steel ring detaches the striker release plate from the striker, permitting the striker spring to drive the striker into the percussion cap.
Used to ignite safety fuse.