Green’s Dictionary of Slang

1. (Aus.) a pony.

1857		‘Ducange Anglicus’ Vulgar Tongue.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1945		Baker Aus. Lang.

2. £25; (Aus.) A$25 [= pony n. (1b)].

1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1960		J. Franklyn Dict. of Rhy. Sl.
1971		J. Jones Rhy. Cockney Sl.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 36: Macaroni Pony, twenty five dollars.
1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

3. a piece of human excrement; thus the act of defecation [pony (and trap) n. (1)].

1974

in J. McVicar McVicar by Himself in DSUE (1984).