A sixpence. The kiddey tipped the rattling cove a tanner for luck; the lad gave the coachman sixpence for drink.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Tangier * Tantadlin TartNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes