Green’s Dictionary of Slang

1. a farthing.

c.1685		‘The Destruction of Plain Dealing’ in Ebsworth Bagford Ballads (1878) I 436: But faith now their calling is not worth a jack.
c.1698		B.E. Dict. Canting Crew.
1709		N. Ward Compleat and Humorous Account of Remarkable Clubs (1756) 234: He could [...] have pick’d up a Hog with more Ease than he now could eight Jacks upon an Easter Holiday.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 207: Jack, a farthing. He would not tip me a jack, i.e., he would not give me a farthing.
1725		New Canting Dict. n.p.: jack a Farthing; He wou’d not tip me a Jack, Not a Farthing wou’d he give me.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
1741		Canting Academy, or the Pedlar’s-French Dict. 113: A Farthing A Jack.
1753		J. Poulter Discoveries (1774) 43: A Meag and Jack; a Halfpenny and Farthing.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum 44: jack A small coin.

2. (US) money.

1807		implied in make one’s jack
1890		M. Townsend Index USA 427: The [...] verbal wealth of the United States language is illustrated in an inquiry for a loan of money; by using any of the following words in conjunction with the inquiry, Have you any [...] Jacks, [etc.] .
1918		R. Lardner Treat ’Em Rough 69: Each one of the boys gets $3600.00 and that would of been my share only I loved my country more than a few dollars and I bet the boys feel kind of ashamed of themself to think I was the only one that passed up all that jack to work for Uncle Sam.
1922		M.E. Smith Adventures of a Boomer Op. 19: I sure would like a piece of ‘Jack’, because if money talks, there is no scandal going on in my pocket.
1939		J. Weidman What’s In It For Me? 340: You’ve borrowed close to 30,000 bucks so far... that’s a lot of jack.
1946		S. Jackson Indiscreet Guide to Soho 104: It is no uncommon thing to see them drop watches [...] and cuff-links in the ‘kitty’ when they run out of ‘jack’.
1950		P. Hoskins No Hiding Place! 191/1: Jack. Money.
1953		J. Thompson Savage Night (1991) 7: All the jack he’d made in the rackets was gone.
1961		T.I. Rubin In the Life 97: Got to get the jack together. Want to go in style.
1974		G.F. Newman You Flash Bastard 63: He indicated the forged bank-notes [...] Sneed produced a genuine five-pound note to compare them [...] He offered them to Feast [...] He took his Jack back from the DS.
1978		(con. WWII) T. Sanchez Hollywoodland (1981) 107: You got more jack than FDR.
1987		‘Joe Bob Briggs’ Joe Bob Goes to the Drive-In 5: A bunch of sleazy guys [...] trying to hustle up enough jack so they can move to Atlantic City.
1997		(con. 1970s) G. Pelecanos King Suckerman (1998) 192: Hook up with Trouble Man, get the rest of our jack.
2001		(con. 1929) N. Tosches Where Dead Voices Gather (ms.) 137: Brown talks of blindsiding his woman, of [...] ‘spendin’ her jack’.
2003		Simon & Pelecanos ‘Duck and Cover’ Wire ser. 2 ep. 8 [TV script] You gonna get a car you gonna need some jack.

3. (also half-jack) a counter, similar in size and shape to a sovereign or half-sovereign, used in gambling houses and casinos [strangely enough, jack and half-jack are gambling counters worth a whole/half a sovereign, and half-jack (below) contemporaneously means a half-sovereign, but jack alone never seems to equal a whole sovereign].

1859		Hotten Dict. of Modern Sl. etc. 52: Jacks and Half Jacks card counters, resembling in size and appearance sovereigns and half sovereigns, for which they are occasionally passed to simple persons. In large gambling establishments the ‘heaps of gold’ are frequently composed mainly of jacks.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 349/2: The ‘card-counters,’ or, [...] the ‘small coins,’ are now of a very limited sale. The slang name for these articles is ‘Jacks’ and ‘Half Jacks’.
1873		Sl. Dict.

4. (US black) a combination of five digits used in numbers, the n.

1928

Yodelling Kid Brown ‘Policy Blues 🎵 It takes five numbers to make a jack, / And you must be born lucky to get your money back .

5. (Aus.) in two-up, a double-headed coin.

1948		R. Raven-Hart Canoe in Aus. 187: Pennies supplied by ‘school’ to avoid ‘nobs’, ‘jacks’, double-sided heads, ‘greys’, double-sided tails.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxv 6/3: jack: A double-headed penny.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 32: Jack Double-headed penny.
1999		G. Seal Lingo 150: Early kips (also called lannets) are said to have been masterpieces of carpentry often with secret compartments used to hide double-headed (nob, jack) or double-tailed (gray) pennies.

6. see jack’s (alive) n.