The RAF transmitting VT501A was later renamed the CV1002. It is a small beam tetrode RF power valve and a variant of the VT501.
The blackened anode connects to the top cap and has a central rib for strength.
The The control grid is fitted with a heat radiating fin at the top. The cathode tube has rounded ends and the bright beam plates can be seen to extend below the anode.
The classic envelope is 32 mm in diameter and, excluding the IO base pins, is 88 mm tall.