Green’s Dictionary of Slang

1. a five-shilling (25p) piece, a crown.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1834		(con. 1737–9) W.H. Ainsworth Rookwood (1857) 231: One quid, two coach-wheels, half a bull, three hogs, and a kick.
1848		Flash Dict. in Sinks of London Laid Open.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict.
1895		Crowe Aus. Sl. Dict. 18: Coach Wheel, a crown piece.
1905		Exeter & Plymouth Gaz. 4 Feb. 5/6: A five-shilling piece was once known as a ‘coachwheel’.

2. (US) a silver dollar.

1812		Vaux Vocab. of the Flash Lang.
1859		Matsell Vocabulum.
1881		Trumble Sl. Dict. (1890).