A common fraud, thus practised: A fellow drops a brass ring, double gilt, which he picks up before the party meant to be cheated, and to whom he disposes of it for less than its supposed, and ten times more than its real, value. See Money Dropper.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Faytors * FawneyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes