The VT-33 is the US Government code for the commercial Type 33 battery audio output pentode. Under normal conditions, operating as a single ended class A amplifier the output is 700 mW.
The box anode from the side.
The pinch end showing the oxide coated filament and the three wire grids within the anode.
The UX5 base pins.
The classic envelope is 44 mm in diameter and, excluding the UX5 base pins, is 102 mm tall.
References: Data-sheet, 1043. Type VT-33 was first introduced in 1936. See also1936 adverts.