I don't recognise this engine and would be grateful for information from anybody who does. From the same collection as the Westbury "Kittiwake" I have, this is a disc-valve two stroke with water-cooled head. It has an oil pump and appears based on commercially-made castings. Turns over easily, good compression and comes complete with a noisy-looking exhaust pipe!
I would estimate the capacity at about 30cc.
Height 9 inches