Is there an "H" stamped on the top of the flywheel at the nut? Look at the front of the carb and see if there is an "H" there and is there an air manifold on the back of the engine between cylinders? Check and see if the serial number stamped on the base of the crankcase matches the one on the tank. It does not have the gearfoot that was used on the high speed model.

George