Green’s Dictionary of Slang

1. a sovereign, thus latterly £1 sterling.

1821

D. Haggart Autobiog. 100: I got eighteen quids, good British Linen boys, and a scout.

2. (US) a note, for one dollar, ten dollars etc.

1899–1900		C.L. Cullen Tales of the Ex-Tanks 82: The lowest I’ve got here is one of the five-hundred dollar boys [i.e. a note].
1902		C.L. Cullen More Ex-Tank Tales 108: He peeled me off seven of the one hundred boys.
1961		R. Gover One Hundred Dollar Misunderstanding 22: Ain you got no skins, no kale? No bread? No bones, no berries, no boys?