Green’s Dictionary of Slang

(Aus.) in horse-racing, a favourite; a horse tipped to win; also used in non-racing contexts (e.g. cite 1936).

1926		Sun. Times (Sydney) 21 Nov. 8/3: [advert] While most people were asleep we caught a ‘Toby Roacher’.
1932		Referee (Sydney) 20 Jan. 5/3: [advert] The ‘TOBY-ROACHER’ for Anniversary Day will not be 20 to 1 . No 20 to 1 chances from me. [...] The horses I have tipped were even money chances.
1936		Carins Post (Qld) 4 Sept. 1/5: AH! Hal Hal What you can't get on the Swinging Boat you can get on the merry-go-round at our joint. Cars, Trucks, Utilities, Refrigeration [...] and, Boy, the Toby Roacher of them all the world famous Caterpillar Tractor, the machine that pulls you through.