Green’s Dictionary of Slang

John Dunn n.¹

(Aus.) £1.

1895		Western Champion (Barcaldine) 31 Dec. 9/5: A profitable profession it seemed, too, judging from the cool way they talked of ‘John Dunns’ (£1), ‘thick ’uns’ (sovs.), ‘canarys’ (halfsovs.), ‘finn’ (£5), &c [AND].
1905		Shearer (Sydney) 4 Mar. 4/1: It would be interesting to know how many ‘working-men’ in this country [...] are in receipt of three ‘John Dunns’ per week all year round [AND].