Trench Art Shell Lighter (WW I) . The head is copper and the shell casing is brass. It com apart in 2 pieces. Inside the casing is a lighter. The shell is marked: "37-85 / PDPs 17_1_18" PDP stands for the factory, “Pouderies de Paris”, and 37-85 means 37mm model of 1885. The 17.1.18 is the manufacture date, 17 January 1918. The 256 signifies the serial number. The M1916 37mm gun was developed by the French and used primarily by French and American forces in WW I for destroying machine gun emplacements. It was fairly good at this under fluid, mobile conditions, but inferior to mortars for static trench warfare. It was still in limited service by World War II, but generally relegated to training and use as a sub-caliber addition for larger guns. Ammunition was of two types initially, a 1-pound solid steel shell and a high explosive round. The solid round was found to be largely ineffective, and replaced with a bursting shell of cast iron and filled with black powder. Mounting for the gun was either a fixed tripod or wheeled carriage. Mechanically, the M1916 used a rotating breechblock and hydraulic recoil absorber coupled with a spring recuperator. In addition to use as an infantry gun, the M1916 was also mounted in the early US M1917 Renault tank.