The CV1503 is an audio output pentode/beam tetrode based on the M-OV KT33C. The old RAF service code is VR503.
The internal coating obscures the inner detail but the shape of the anode can be seen.
The pinch end: the cathode is rectangular, the heater passes four times through the cathode and as formed from insulated coils of wire. The control grid is wound on copper supports.
The top mica: the control grid heat sinks and the S shaped ribbon connects the beam plates to the cathode.
The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 103 mm tall.
Reference: Data-sheet. Type CV1503 was first introduced in 1938. See also1938 adverts.
