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.
This exhibit is unbranded but carries the UK Government up arrow.
The construction has the triode mounted above the screening box that houses the two vertical rods of the diode anodes. The pinch and pinch stem can be seen with the hole for the evacuation tube.
Seen from the side the top mica has springs attached to hold the assembly firmly within the shoulder of the glass envelope.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 98 mm tall.
References: Data-sheet, 1040 & 1043. Type DH63 was first introduced in 1937. See also1937 adverts.