OK, here's the short version!
Its scratch built, based loosely on 'Skookum' which was a small standard gauge Mallet but I've altered the cab proportions slightly to make it look Narrow gauge.
Chassis uses Big Hauler wheels in a brass frame with LGB motor in rear unit only - I only have a small track and don't need more power. Body is built round a piece of 3 inch plastic pipe with plasticard for the rest of it, both power units pivot so it will go round a first radius curve although it looks ridiculous doing it!
I made it in 2004 so it's lasting well although some of the smaller valve gear parts were plasticard and are now becoming brittle, time to redo them in brass I think.