I have always thought that the No:4 tail unit for the 2inch inch mortar was a post war replacement for the wartime No 3 steel tail. When I went to the War and Peace show Sat I was lucky to pick up 3 very mint 2 inch para illum rounds and a multi white star round, two of the rounds were dated 1944 and one dated 1943.One of the para illum rounds still had its original parachute dated 1942. What I did notice that two rounds had No:4 tail units one dated 1944 and the other dated late 1943, quite a surprising find, puts my theory out of the window, anyone here have an earlier dated No:4 tail unit.