Hi brisy, well the ID Plate confirms it, it is a Rover and that combined with the manufacture date of the Briggs and Stratton, which is 7th October 1981 means that Scott Bonnar had been merged into Rover Australia LTD by that date. They were then known for a time as Rover-Scott Bonnar.
As I stated earlier, my belief is that Scott Bonnar did not have ride-ons as part of their line-up at any stage, prior to the take-over by Rover.
In my opinion, your machine is a Rover Colt 5, Model 72721, manufactured by Rover-Scott Bonnar in late 1981 early '82. wink
Are you planning to restore it....I think it would come up a treat! grin
cheers2

Please do not PM me asking for support. Please post your questions in the appropriate forums, as the replies it may receive may help all members, not just the individual member.
Kindest Regards, Darryl grin