The CV4002 is the flying lead version of the CV4014. Electrically it is an M8083 or 6064. These are both designations for the special quality version of the EF91 (CV138).
The special quality version has a more rugged build than the EF91 and was designed for operation in areas of vibration especially aircraft.
The KB/AD identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the AD identifies the maker as Brimar - Thorn-AEI , Rochester.
The internal coating on the glass suppresses the effects of electron bombardment.
Unlike the valves made with later additions of tags, this was made with the wire exiting the glass base and would be directly soldered into the circuit. Only possible with valves designed for a long service life.
Some internal details are visible. The heater passes several times through the flattened cathode tube. The control grid is wound on copper rods.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
Reference: Data-sheet. Type CV4002 was first introduced in 1953. See also1953 adverts.
