Hi there I'm new to the site. I own a 1979 8011 myself which runs like a clock. I was just enquiring about the 8011 S a local contractor used to have one which he used to run with a a rusty old green claas rotary drum mower in his Silage contracting business and I visually inspected it a few times, when he left it parked in our place, and could see no discernible difference to my own. What does the "S" mean.