Rex, Garelli, and Moto Parilla all used the same 125 cc 4 stroke in the mid 1960s (like around 1965). I think the parilla was called the wildcat scrambler and the Garelli was the KL125. It should be a pushrod engine IIRC. A buddy of mine had one in boxes in new orleans I thinkt he brand in america was "Rex Garelli" but I have seen them sometimes called just Rex or Just Garelli. By the mid 1960's I think Garelli and Parilla were the same company.
That is Def the Parilla/Garelli generator cover - you don't forget a graphic like that.