A finely made Stuart triple expansion engine, the work of a retired professional engineer with many fine engines to his credit. I had his 3 1/2 inch gauge Stanier tank in a couple of years ago, this engine came in with a Red Wing open crank engine and an absolutely beautiful 9 cylinder Bentley BR2 rotary engine (currently up at the house, having caught Mrs P's eye) which he built.
Pictures tell the story on this one. It's been run on air but never steamed, still feels as-new mechanically. Fitted with Stephenson's reversing gear, air pumps and twin impulse valves for starting the engine when the HP cylinder is on dead centre. There's a clip of it running in the workshop here.
Length 9 1/2 inches
Height 8 inches