Green’s Dictionary of Slang

(Aus.) a police officer, a detective.

1936		Western Argus (Kalgoorlie, WA) 8 Dec. 32/1: A policeman the other night was to be seen with that rara avis — a light on a police bicycle. [...] Another ‘hot scone’ on Thursday afternoon rode up Maritana bridge and coasted down the other side with both hands off the handle bars.
1941		Baker Popular Dict. Aus. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.