This is an experimental Solenoid valve. The tag on the machine made glass envelope is number 5. Hanscomb working for QRS made a series of tests looking for an improved 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.
Updated August 05, 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