Half a pint. Size of bread and cheese; a certain quantity. Sizings: Cambridge term for the college allowance from the buttery, called at Oxford battles.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Sixes and Sevens * To SizeNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes