This is W112 from Dixon. This cartridge was developed by Adam Schurk, a Munich based gunsmith, in the late 1930’s and developed by necking down a 6,5 x 57 Mauser case (DWM J J K 404A K and R.W.S.  N. and RWS 6.5×57). The intervening war and death of Adam Schurk put paid to the project. The cartridge was further developed in the early 1960’s by RWS before being commercialised in 1964.  All the prototypes exhibit much longer necks than the commercial cartridge.