Green’s Dictionary of Slang

(N.Z.) one shilling (5p).

1952		Argus (Melbourne) 13 June 4s/3: Here we have the ‘John Dillon’, and [...] ‘hammer and tack’ for ‘zac’ (6d.) and ‘Rhodes scholar’ for ‘dollar’ (5/-).
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1988		McGill Dict. of Kiwi Sl. 63/2: John Dillon a shilling; rhyming slang, c.1930, but also name of a well-known racehorse.
1992		R. Puxley Cockney Rabbit.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].