Holy cow, you solved a mystery I thought I'd never learn! This whole affair registering and posting has paid for itself on your "Sears" fact! I seen lots of these little engines around for sell and never saw any with the throttle and it confused me ... a LOT!
Which makes total sense; as my grandfather, my dad and me bought *everything* from Sears (up until Sears burned me on an extended warranty on my lawn mower in 2002).
Thank you for that fact on my engine!