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 side view shows the oval anode. It is left bright as it handles very little power. The maximum output in class A and at 6% distortion is only 270 mW. This seems small but when transistor radios appeared in the mid 1960's the 250 mW output was commonplace and coupled to a tiny (or tinny) two or three inch speaker. The wooden case battery radios of the DL33 era would have at least a five inch speaker mounted on a wooden baffle.
The top view is distorted by the glass. Apart from the top mica the two filament springs are seen.
The wide glass tube envelope is 30 mm in diameter, and excluding the IO base pins is 75 mm tall.
References: Datasheet, 1040, 1043 & 3002. Type DL33 was first introduced in 1946.