WW2 SOE Number No.10 Mk.I Delay Switch

A British Number Ten Delay Switch (official name, "Switch, No. 10, Delay" and often referred to as a "timing pencil"), was made of a brass (or in later versions aluminium) tube, with a copper section at one end which contained a glass vial of cupric chloride (the liquid was widely and erroneously reported to be sulfuric acid), while beneath the vial was a spring-loaded striker under tension and held in place by a thin metal wire. The timer was started by crushing the copper section of the tube to break the vial of cupric chloride, which then began to slowly erode the wire holding back the striker. When the wire eventually parted, the striker was propelled down the hollow centre of the detonator, hitting the percussion cap at the other end of the detonator.

Code: 51434