The DH63 is a double diode triode with the control grid brought to the top cap. The design use was as detector and ACG rectifier together with first audio amplifier stage in receiver equipment.
The DH63M was the metalised version.
In this specimen the internal construction is obscured by the internal coating but in the classic envelope of 6Q7G the construction becomes visible. This valve was also made in the GT form and we have a specimen in 6Q7GTY.
The MWT label of Marconi's Wireless Telegraph company.
The pinc and supports are the only parts clearly visible.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 91 mm tall.
References: Datasheet, 1040 & 1043. Type DH63 was first introduced in 1937.