This exhibit is another Atlantic and Pacific Co. Electron Relay. This has a different anode design that is usually known as 'Short and Shiny'.
The design uses a single anode support and as a result the valve was microphonic.
The original box for this exhibit. Like many others the box size was 50 mm square and 128 mm tall.
Thanks to Joe Gruber for sending the images.
The balloon envelope is 44 mm in diameter and, excluding the UV base pins, is 104 mm tall.
Reference: Joe Gruber.
Updated February 08, 2021.