hi i have an original operators manual for one of these.
What a fine looking mower you have there!
Its designed and manufactured by John Boundy industries pty ltd Clayton, Melbourne, Vic and Eagle Farm Road, Brisbane. Don't know if they made the engine? Its a unique engine with a crankcase magneto. Manual says 20 parts petrol to one part SAE 40 oil. Also have a full page advertisment from The Sun-Herald dated march 17, 1957 It advertises the Lawn Scout and the Lawn Cub. The lawn cub is a 15 inch cut (80cc 1.7 BHP) priced at 36 Gns. Re the muffler, it also says "Triple expansion exhaust silencer of pressure cast aluminium, quitest on the market"

cheers
matt