Been having a chat with a forum member about 3inch 20cwt cases Mk11 and MkV, the Mk11 inquestion date is 1916 and the MkV 1938. I know that the 3inch 20cwt was used as a AA round during the first Blitz during WW1 and also as a Naval round on ships as well most probably after 1945. What would be the differences in the case Mks. Were WW1 cases refurbished and used during WW2.