Hi jackg, and a warm welcome to the forum. It's great to have another Scott Bonnar owner on board.
I would have to agree with you, this machine was a steal at $85.00...Good score there mate!
Both Bruce and grumpy are spot on, it is indeed a very late Model 45, so late in fact, that I suspect it was assembled by Rover...the clue being the solid light green colour and the black Briggs and Stratton, this colour scheme was used by Rover instead of the olive green hammertone, of the earlier Scotties. I have to agree with grumpy though, I have not seen a Briggs without its stickers, they may have come off if the machine was pressure washed at some stage...I have seen that happen.
Now to the chassis...it is a 17" cut, 6 blade cylinder reel which, as grumpy has said, appears never to have been spin- ground, without a pic of the underside I cannot tell the condition of the bottom knife-blade.
Some observations; you are missing a left-hand grass box (catcher) support rubber (opposite the height adjuster)which helps stop grass box vibration. Also the grass deflector needs to be aligned correctly.(just undo the 2 black knobs on the top of the front rail and push the deflector up and in, until it is square with the rail. This controls how the grass is directed into the grass box).
The vibration through the handlebars would be caused by the engine running roughly and once that is sorted, should be rectified. The machine will come up a treat once cleaned, and with the engine running sweetly, should give you hours of mowing pleasure.
Once again, jackg,
