The POVT37C is a directly heated voltage amplifier triode based on the E1532. The design was made for the UK General Post Office GPO at the time controlled directly by the government. Originally called VT37C it was officially re-styles POVT to avoid confusion with the RAF use of VT for Valve Transmitting. With the advent of the CV register in 1941 it was re-named CV1644. Both designations are on the envelope.
E1532 is an M-OV experimental code and the lozenge containing the Type designation is clearly M-OV.
The bright anode of the triode with filament tension springs above the top mica.
The box anode with the grid winding within. The tension springs are held in a glass rod.
The four strands of the filament.
The UV base - much used in telephone repeater equipment.
The balloon envelope is 50 mm in diameter and, excluding the UV base pins, is 102 mm tall.