The DV-3 is a triode from De Forest that appeared in about 1925. It features a 3.0 Volt filament for use with dry cells. For dry cell use the filament must be a low consumption type, so not a bright emitter.
Thanks to Dan Absher for the picture and information.
The wide glass tube envelope is 32 mm in diameter, and excluding the UV base pins is mm tall.
Reference: Bill Condon & 1047. Type DV-3 was first introduced in 1925.
Absolute Maximum Operating Conditions¶
Updated September 19, 2020. shape:wide.glass.tube construction:pinch type:triode age:1920.1930 base:uv pins:4 pin:1.f pin:2.a pin:3.g1 pin:4.f