Green’s Dictionary of Slang

eight shillings (40p).

1859		Hotten Dict. of Modern Sl. etc. 130: TEAICH-GUY, eight shillings,-a slight deviation from the numerical arrangement of gens.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 23/1: The exception to the uniformity of the ‘gen’ enumeration is in the sum of 8s., which instead of ‘teaich-gen’ is ‘teaich-guy.’.
1870		Hotten Sl. Dict. [as cit. 1859].
1935		R.T. Hopkins Life and Death at the Old Bailey 66: [as cit. 1861].