The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
Looking along the grid axis. The vertical sheets are part of the anode. The cathode tube is wide and has a small front to back measurement, The grid passes very close to the cathode and the grid wires are very fine. The grid seems to be wound on two rod supports rather than a frame grid.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 41 mm tall.
References: Data-sheet & 1040. Type CV5112 was first introduced in 1956. See also1956 adverts.
