Hi grumpy, well spotted mate, you are right, it is a late model Scotty (and may I say in very good condition except for the handles) but I think I know the reason for the Kirby being fitted...it is the small 14" machine and the Kirby is a 2HP; the 17" has the 3HP Briggs....maybe Briggs did not have a 2HP engine that was suitable or available at the time...
But the mystery doesn't stop there....if you have a look at the decal on the handle cover plate, it is the older style....it should be orange and the Scott Bonnar in the same design as my avatar above....and the same on the catcher....
