This is a very early Edison Effect lamp made in 1885 for Professor Fleming at London University. It is believed to be one of the earliest valves ever made.
This exhibit was sold to the late Tony Hopwood, an expert in early electronics and a long-time collector of Edison memorabilia, by Dolby Jones.
The filament with the metal collecting plate between.
The electrodes are sealed into a lamp pinch and within the stem are insulated by ceramic tubes.
A close-up of the pinch and the base of the electrodes. The broken single strand filament looks to be secured to the support by copper tape.
The balloon envelope is mm in diameter, and excluding the base wires is mm tall.
References: Anthony Thornton-Hopwood. Type Edison Effect was first introduced in 1885.
Updated March 16, 2016. shape:balloon construction:all.glass type:diode age:pre.1920 base: pin: