Green’s Dictionary of Slang

C n.²

(US) $100.

1837		N.Y. Herald 9 May 2/3: V’s, X’s, L’s, and C’s of the Dry Dock Bank.
1846		S. Smith Theatrical Apprenticeship of Solomon Smith 149: So there’s my hundred — and as my pocket-book’s out, and my hand’s in, there’s another C [DA].
1874		Chicago Trib. 7 Aug. in A. Pinkerton Reminiscences (1879) 204: Brown [...] laid a C with the Texan clown / And eke the same did win.
1884		Chicago Trib. 25 May 13/4: One man got up from a roulet [sic] table $100 winner [...] ‘[N]ow that I have reached a C I’ll vamose’.
1899–1900		C.L. Cullen Tales of the Ex-Tanks 169: He tripped me a ‘C’ from his roll.
1929		Hostetter & Beesley It’s a Racket! 221: c — One hundred dollars; hundred dollar banknote [...] ½ a C — Fifty dollars; fifty dollar banknote.
1938		D. Runyon ‘Pick the Winner’ in Runyon on Broadway (1954) 322: Herbie explains that five C’s is five hundred dollars.
1944		C. Himes ‘Let Me at the Enemy’ in Coll. Stories (1990) 38: At first I was thinkin’ in the C’s; knock seven or eight hundred then jump down.
1957		C. Himes Imabelle 5: You give me fifteen C’s – right?
1958		R. Prather Scrambled Yeggs 67: I’d have bet the ten C’s in my wallet against a two dollar win ticket on Stupendous.
1965		C. Himes Rage in Harlem (1969) 7: [as 1957].
1970		E. Thompson Garden of Sand (1981) 137: But a man with only one hundred dollars don’t pack it around in a single C-note.
1986		Big Audio Dynamite ‘Sambadrome’ 🎵 I paid you five Cs of my hard-earned cash.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 90: Pete slid him two C’s.

In phrases

half-a-C (n.) (also half-C)

(orig. US Und.) a 50-dollar note.

1936		(ref. to 1918) L. Duncan Over the Wall 21: I learned quickly that a dollar bill was a fish-skin [...] fifty a half-a-C.
1947		N. Algren Neon Wilderness (1986) 206: I put a half-C in your wallet.
2001		ONDCP Street Terms 11: Half-a-C — $50 bill.