This exhibit is an experimental Fleming diode. The valve is original but the frame mount is new. The Valve Pioneer article above has an image of an original frame.
Sir Ambrose Fleming had these diodes made so that he could investigate the Edison Effect. These experiments later were re-conducted with the aim of making a sensitive radio detector.
The commercial product using his ideas can be seen in Fleming.
Thanks to Joe Gruber for sending the images.
Updated July 06, 2021.