The DL33 is a dry battery audio output pentode. The directly heated filament is only rated for DC use. Even at 1.4 Volts the AC hum would be impossible to live with.
The original maker is Mullard and in this exhibit Bentley have not wiped the original lettering before adding their own label. The UCL82 shows their normal re-branding.
The Bentley label.
The actual pentode occupies only a third of the envelope with considerable space taken by the pinch stem.
The top mica. The filament is two independent strands with the loop that secures the tension springs being at half voltage and connected to g3.
The wide glass tube envelope is 30 mm in diameter, and excluding the IO base pins is 75 mm tall.
References: Data-sheet, 1040, 1043 & 3002. Type DL33 was first introduced in 1946. See also1946 adverts.