The DH63 is a double diode triode and was designed for receiver audio use.
The diodes would be for signal and AGC rectification and the triode would act as AGC amplifier or first audio amplifier.
The Marconi paper label.
The triode sits above the screen that conceals the rod anodes of the double diodes.
In this image the connection between the diode screen and the cathode can be seen. The diode anodes can be seen as two vertical rods either side of the heater connection.
The classic envelope is 39 mm in diameter and, excluding the IO base pins, is 101 mm tall.
References: Data-sheet, 1040 & 1043. Type DH63 was first introduced in 1937. See also1937 adverts.
