Green’s Dictionary of Slang

(Aus.) dead right.

1945		Townsville Daily Bull. (Qld) 3 Dec. 2: Sandy blight, to boomerang, within cooee [...] have found useful and apparently permanent niches in our vocabulary.
1972		G.W. Turner Eng. Lang. in Aus. and N.Z. 101: Sandy blight (the name of an eye-disease common in nineteenth-century Australia), for ‘dead right’.