German made Trip flare.
The body has brown transport plug covering a percussion cap. This cap is waterproofed with green lacquer.
A trip wire is attached to a paper clip.
In safe position the paper clip is closed. After installation of the mine, in „armed” position the paper clip is opened.
Pulling the trip wire, the paper clip will release a striker, which hits the percussion cap initiating the signal trip flare.
A complete trip flare set includes the attachment base, brown string (trip wire), two nails, striker mechanism and a paper clip.
Explanation and photos thanks to L.B.