The VU33 (later the CV1033) is a directly heated oxide coated filament signal diode. The old UK military stores code of 10E/9829 is also etched into the glass.
The problem is that this valve has a grid that connect to a base pin. The stores code points to CV1033 and VU33, so it correctly identified. One diagram shows the grid connected to the anode.
The A M and crown of the UK Air Ministry.
The Cossor name on the dome and the grid within.
Here it can be seen that one of the filaments is broken and one of the tensioning springs is missing.
The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 90 mm tall.
Reference: Data-sheet. Type VU33 was first introduced in 1935. See also1935 adverts.
