Interesting. My notes from about 1979 do not say what their intended purpose was. I think they were designed to be fired from a 1.5 inch calibre weapon, perhaps similar to an anti-riot gun. The Cart Illum 1.5 Inch J Mk 4T was designed to be fired from a signal discharger or Pistol Signal No 4 and I presume that those weapons could also fire the other cartridge variants. The Illum had a five second delay to ignition and burned for 9.5 to 11.5 seconds. It had a paper case with a brass cartridge head. The star comprised five pressings of Gunpowder (GP) G12. The propelling charge was 31 grains of GP G12. The star extended 1.9 inches out of the cartridge case.. There was a white paper label on the end, bearing the word `Illum' in blue.
There were three types of 1.5 inch signal cartridge, each having one star: Green Mk 7T; Red Mk 7T; Yellow Mk 4T. These each had a 46 grain GP G12 propelling charge, an 1100 grain star filling with primed cambric at both ends. The star was housed in a light gauge tinplate container. The whole was contained in a paper cased cartridge. Markings consisted of a coloured band around the case and a label on the top.
A kind of modified / specialised use was determined for explosive demolitions where telephonic communication was not possible. Smoke puffs could be used at the firing point where: Cart signal 1.5 inch green meant `Stand by' meaning that there would shortly be an explosion; Cart signal 1.5 inch white smoke puff meant `firing', ie detonation now; Cart signal 1.5 inch brown smoke puff meant `Misfire' and Cart signal 1.5 inch illuminating meant `All clear'. This system was not authorised for use if the method of disposal was by burning.
The brown and white smoke puffs each came in two Mks: Mk 3T and Mk 4T and the cartridge case was marked with a serpentine symbol in the colour of the effect produced ie brown serpentine symbol or white serpentine symbol running down the length of the case. Each had `brown smk puff' or `white smk puff' in blue marked on the guilding metal head of the cartridge case. The Mk 3T had a paper case, brass cartridge head stepped where the star extended from the case, 31 grain gunpowder propelling charge with a 1.5 second gunpowder delay charge, igniter of sulphurless gunpowder and 1700 grain smoke composition. The Mk 4T differed by having a cartridge case that was not stepped, the cartridge head was of guilding metal, 15 grain gunpowder propelling charge, and a different delay assembly.
