A Swan Double Two launch engine - I think the design was by Nick Stothard, based on an earlier Clarkson engine although I'm sure somebody will correct me if they know otherwise.
A large, powerful engine - originally intended for a boat, it would be equally suitable for use in some kind of steam car, generating set or something similar. It is a double high engine, self-starting with Stephenson's reversing gear. The engine runs on air, although the reverser still needs a small amount of work to complete - basically provision of a handle and detent mechanism.
Length 21 inches
Height 15 inches
Flywheel 5 inch diameter
Weight est 100 pounds