The Two in One has a double electrode structure (filament, control grid and anode). This sample has a chrome base cap and barium gettering and also a machine made envelope.
The original box measure 50 mm square and is some 128 mm tall. This is a later redesigned box with better information.
Thanks to Joe Gruber for sending the images.
The balloon envelope is 44 mm in diameter and, excluding the UV base pins, is 104 mm tall.
Reference: Joe Gruber. Type Two in One was first introduced in 1919.
Updated August 04, 2020. shape:balloon construction:pinch type:triode age:pre.1920 base:uv pins:4 pin:1.g1 pin:2.f pin:3.f pin:4.a