The CV858 is the UK service designation for the 6J6. This miniature double triode was used for VHF signal amplification.
The construction has a common flattened tube cathode, with the control grids either side.
The KB/D identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the D identifies the maker as Mullard Radio Valve Co., Mitcham.
The anodes are U channel sections either side of the central cathode. At first sight the valve appears to be a single device.
The central white coated cathode. The single sided grids are shaped to pass flat in front of the cathode.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins is 46 mm tall.
References: Data-sheet & 1040. Type CV858 was first introduced in 1956. See also1956 adverts.
