This exhibit is a standard production US Navy CG-1787. Bakelite base cap with horizontal ink lettering. Rainbow getter.
The base cap.
Thanks to Joe Gruber for sending the images.
The balloon envelope is 35 mm in diameter and, excluding the UV base pins, is 98 mm tall.
Reference: Joe Gruber. Type CG-1787 was first introduced in 1918.
Absolute Maximum Operating Conditions¶
Updated March 07, 2020. shape:balloon construction:pinch type:triode age:1920.1930 base:uv pins:4 pin: