This is the middle sized engine made by Eric Jeanerette for Walther & Stevenson. It stands 10 inches tall with its Chimney and cost 15/- in 1935. Notice the similarity of this engine to the Scorpion Verticals which W&S sold after the war. Its very likely that this engine gave the inspiration for the Scorpion verticals.
Here is my own example of this engine that I have yet to restore and is missing its chimney.