The engine is the so called “ashtray head”. The cylinder and head are designed for the US market. It replaced the earlier, classic Aermacchi cylinder/head. Customers in Europe didn’t like that design much and so it was available in Europe just for a short time period from 1969 to 1970 before they changed back to the classic knucklehead with the 1971 models. In US they kept the ashtray design until the arrival of the 1973 model of the Harley-Davidson Sprint.
Engine crankcase: L988