OK, that really is different. I'm guessing that the double sprocket directly driven by the engine sprocket is just an idler, it isn't connected to anything. That makes it possible to change the drive ratio from the engine to the reel, and everything that comes after it. I've seen some complaints here from ATCO owners who didn't like the mower's forward speed, so maybe this was a design change from ATCO - or maybe a cobbled job done by a former owner.
