I saw this engine for sale recently at a modelers home, and am wondering what size and brand it is? It is a twin-cylinder and has dark red cylinder heads. On the engine itself, there is stamped a logo with the letters "AOH". The "O" has a propeller underneath it. It has a twin carb setup, and also has a very large strange-looking circular backplate -- solid, thick metal. There were no other numbers or markings on it -- I Googled "AOH" but came up with nothing.

Any help would be appreciated!

Thanks,
Garret H