It is a variation of the well-known percussion cap or fuse by which mines and torpedoes are exploded.
"Elusive Isabel" by Jacques Futrelle
The fuse is time and percussion.
"Scientific American Supplement, No. 586, March 26, 1887" by Various
One of the men inserted a percussion fuse in the touchhole of the mortar.
"Larry Dexter's Great Search" by Howard R. Garis
Of course percussion-fused shells falling on ploughed land seldom burst, as a boy here found by experiment.
"Ladysmith" by H. W. Nevinson
PERCUSSION FUSE FROM 1-LB.
"Surgical Experiences in South Africa, 1899-1900" by George Henry Makins
The next move was for the Yankees to change from percussion to time fuses.
"The Story of a Strange Career" by Anonymous