This exhibit is a Moorhead VT-B experimental transmitting valve. The base is a standard US Shaw type known as UV. The standard base was used as it easily facilitated testing.
Thanks to Joe Gruber for sending the images.
The balloon envelope is mm in diameter and, excluding the UV base pins, is mm tall.
Reference: Joe Gruber. Type VT-B was first introduced in 1917.
Updated September 20, 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