Here we have a De Forest Type T tubular audion. The valve has flying leads but this example has the candelabra socket adapter that the glass tube fits into. See the attached data-sheet for a drawing of the two separate parts.
The paper label on the glass dates to 1916. The anode is an open cylinder and the control grid is helical and looks to be made of copper.
As a bright emitter the filament is connected to a six volt accumulator via a rheostat. The rheostat would be connected with maximum resistance in circuit and gradually altered to increase the filament brightness. To maximise the life of the filament the brightness should only be set to the minimum required for good reception.
Thanks to Joe Gruber for sending the image.
The thin glass tube envelope is 20 mm in diameter and, including the base, is 111 mm tall.
Reference: Data-sheet & Joe Gruber. Type Audion Type T was first introduced in 1916.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated September 22, 2020. shape:thin.glass.tube construction:pinch type:triode age:pre.1920 base: pin: