Text copied from TM9-1985-2 German Explosive Ordnance 1953 :

Description: The igniter consists of a thin aluminium alloy foil drum containing a glass ampoule of sulphuric acid and a white powdered flash composition containing naphtalene. The drum is crimped to facilitate crushing from vertical pressure. The glass ampoule is fized to the top of the drum with pitch. A waterproof paper disc confines the flash composition powder in the igniter and prevents moisture from entering. The drum is secured to the brass base by crimping and a rubberized washer is placed around the threaded portion of this base. The thread is standard and will fit any German booby trap and demolition device.

Operation: When pressure is applied, the foil drum is dented and the ampoule is broken. The sulphuric acid contained in the ampoule mixes with the powdered flash composition and the flash resulting from the chemical reaction fires the detonator.

Employment: This igniter has been used principally with the antipersonell "pot" mine, but is adaptable for use with any type of German booy trap or demolition device.

Photo below ©
Dave Sampson.

Above: this drawing shows a second model which has its glass ampoule laying on its side instead of standing up.
Does this model look the same on the outside?

Photos below show a group of dug buck-fuzes.
Most of them have a brass base as shown in the drawing.
I have some that are made of white plastic. No documentation so far on this model.