When I grew up all homes were heated by coal fires. Back then it seemed all fire places had a shell casing that was used to house the poker and our home was no exception. I am fortunate that I still have our shell casing but it is no longer used for a place to keep the poker, now it is used as a door stop. My grandfather Alfred Maunders returned from France with my 13 pound casing, I have rubbed talcum powder into the base to make the indentations more readable. From what I understand it is a 1916 manufactured 13 pounder case by Royal Laboratories (Woolwich). C.F. = Cordite Filled. The primer is dated with October 1917 as the manufactured date. The 13Pounder AA Gun was originally a 13 Pounder Field Gun as used by the Royal Horse Artilley but due to its range limitations 5,900 yards it was thought that it would be suitably employed as an Anti Aircraft Gun, which in fact was very successful. The Royal Horse Artillery meanwhile were re-equipped with 18 Pounders. The 13Pounders had a slightly higher Muzzle Velocity than the 18 Pdr. Attached are two pictures of the casing which measures 11.5" tall and is 4" across the base. Also attached is a picture of Duxford's 13 pounder AA gun mounted on a Thorneycroft lorry.