This exhibit is a Delta midget diode fitted with an external grid cylinder.
The Delta Midget Tube Co. of Newark NJ produced valves in 1923.
The spherical part of the envelope is 16 mm in diameter.
Thanks to Joe Gruber for sending the image.
The thin glass tube envelope is 10 mm in diameter and, including the peanut base pins, is 50 mm tall.
Reference: Joe Gruber. Type Delta Diode was first introduced in 1923.
Updated November 26, 2020. shape:thin.glass.tube construction:pinch type:triode age:pre.1920 base:peanut pins:4 pin: