Inside of a Detonator

The detonator has two pipes, one facing forward and one towards the side, joined at one wheel-lock. The mechanism is similar to an ordinary pistol of its day, bar having two pipes. To arm the device you turn the circular wheel halfway with a key and place the cock (known as a Dog) as shown. The dog should hold a piece of pyrite (iron sulfide) that will cause sparks when the wheel revolves.