I'm not at all sure what this one is - the blue paint and St Rollox works plates are obviously meant to convey a Caledonian connection, first thoughts were a scaled up "Rob Roy". It's similar, but not quite.
Silver soldered superheated copper boiler, feed by twin injectors. There has been an axle pump in the past, the pump stay and eccentric sheave remain. Slide valves actuated by Stephenson's valve gear with pole reverser in cab. Sight feed lubricator with tank beneath cab floor. Steam brakes.
A nicely made engine, it goes well.