[Phil G4SPZ]

What a nice item to have in your collection, Peter! I'm sure you're correct in your suppositions.

I hadn't realised that the GWR were actually behind the design of the Heavy Duty model. The GWR seems to have been forward-looking in a number of areas, despite doing a great many things differently from the other railway companies "just because they could". There is a model of Tilley lamp (one of my other hobbies) called the "Challow", named after the Great Western station at which it was trialled during its development, again instigated by the GWR itself. Challow lamps are the holy grail for some collectors, as perhaps the GWR Heavy Duty Avometer should be...