The Two in One has a double valve in the envelope - all electrodes are duplicated.. This sample has a brass base cap and phosphorus gettering. The base cap has both the DeForest and Marconi logos.
The original box measure 50 mm square and is some 128 mm tall. It looks to have a paper label pasted over the original design.
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