Hi Finbar, I can, from the pics, give you some info on your Scotty. Yours is a 14" cut early model 45...This I can tell from the solid engine deck, alloy end caps on the front roller and the brass ID tag.
The 14" Model 45 was first introduced in late 1967/early 1968 and was manufactured at the Thebarton factory in South Australia. It was fitted with a 2HP Briggs and Stratton painted silver. Some may have been fitted with a 2.5hp. engine.
Your machine has also had a new Briggs fitted at a later stage as your Briggs is a 3 HP. manufactured on the 13th November 1979, which is shortly before the take-over of Scott Bonnar by Rover Australia, and the twin rail engine deck Scotties were in full swing!

PS. I wonder what happened to the original engine...
