I did notice that it is a single ring piston so i would assume its an early top end. So maybe it is original? I thought the original xpw's were 75cc, then switched to 71cc later on...??? This is my first husky so I'm still a greenhorn as far as they go. You all know way more than I do about the history and such so maybe you're right. All I know is it says XPW on the tag and all the top end stuff is 50mm. I guessed I just assumed.