This DAC32 is some 17 mm shorter than other Mullard versions. The height matches the Sylvania version but this is a British Made valve and not an import.
The DAC32 is a dry battery diode triode that was designed, after WWII, for AM broadcast radio reception. Mullard describe this valve as a medium gain triode for use as an AF voltage amplifier combined with a single diode for signal or AVC (AGC) rectification.
The filament power is very low and consequently the valve is rated for a very low current.
The triode is at the top with the diode below. The diode anode is the vertical rod to the right of the filament. The bright rectangle is a shield connected to the filament support.
The electrodes seen end on.
In this image the filament can be seen as a single strand but it is not held in tension.
The wide glass tube envelope is 29 mm in diameter and excluding the IO base pins it is 69 mm tall.