Green’s Dictionary of Slang

a guinea or gold coin.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1822		(con. early 17C) W. Scott Fortunes of Nigel II 114: Fifty as fair yellow canary-birds as e’er chirped in the bottom of a green silk purse.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1842		Punch 168: ‘Prolusiones etymologicae’ 13: Goldfinches – Canaries. – Singing birds; the which whose possesseth needeth never to pine for lack of notes [F&H].
1895		Crowe Aus. Sl. Dict. 14: Canary Bird, [...] a gold coin.
1909		J. Ware Passing Eng. of the Victorian Era.