The DH63 is a double diode triode designed for receiver audio use. The DH63M is the same valve with external metallisation.
The diodes would be for signal and AGC rectification and the triode would act as AGC amplifier or first audio amplifier. This is a miniature glass tubular version of this valve, we also have the older version DH63 with the classic glass envelope.
The Osram paper label.
The side view: triode above and diode anodes below.
Each diode anode is on one side of the common cathode tube. Together they look like a single box anode. The triode requires cooling and thus the anode is carbonised.
The wide glass envelope is 27 mm in diameter and, excluding the IO base pins, is 80 mm tall.
References: Data-sheet. Type DH63 was first introduced in 1937. See also1937 adverts.