The CV1644 is a directly heated triode based on the E1532. The old GPO code is POVT37C.
The KB/Z identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the Z identifies the maker as MO Valve Company, Hammersmith.
The CV Type designation and a side view of the box anode. The UV base is a bayonet type and so a locating pin is required on the base shell.
The triode with the filament passing through the grid four times.
The balloon envelope is 50 mm in diameter and, excluding the UV base pins, is 102 mm tall.
