The snowboy that you have is a model SB-13 just like it says on the tag. This is a 1960 model and uses the C12AA engine. The on off switch work by rotating it left for the off position and right for the on position this allows you to start the snowboy in the on position and turn the engine off by rotating the switch to the off position. Also when you have the switch in the on position you can pull up on the black knob and when you have this out all the way this will be in the "full" choke position. Nice machine. I have several snowboys they are my favorite.