Green’s Dictionary of Slang

class adj.

(orig. US) stylish, impressive, superior.

[UK]C. Rook Hooligan Nights 36: A smart youngster, who had done something class in the way of nicking.
[UK]‘Doss Chiderdoss’ ‘A Wordless Play’ Sporting Times 10 Nov. 1/4: The girl of course divinely fair / The gent distinctly ‘class’.
[UK][perf. Vesta Tilley] Seaside Walks 🎵 He’s quite ‘class’ till Maggie Ann joins in the talk.
[Aus]E. Dyson ‘At the Opera’ in Benno and Some of the Push 87: Neither of them had been to grand opera before, but Mr. Dickson understood ‘The Valkyrie’ was ‘class.’.
[US]R. Lardner ‘Three Kings and a Pair’ in Gullible’s Travels 48: But he had hair and two eyes and a mouth and all the rest of it, and his clo’es was certainly class.
[US]B. Hecht A Thousand and One Afternoons [ebook] But he's got a good face, you might say. Class, eh? You'd know he was a musician.
[US]C. McKay Gingertown 11: I wantcha to fohgit him and that no-class gang.
[UK]G. Greene Gun for Sale (1973) 13: You see, she’s class.
[UK]G. Greene Brighton Rock (1943) 88: They don’t like serving me in there; I’m not class.
[US]H. McCoy Kiss Tomorrow Goodbye in Four Novels (1983) 156: This girl beside you now [...] This one’s class. This one’s quality.
[US]W. Brown Monkey On My Back (1954) 27: He had thought of her as ‘real class’ and had been dazzled by his good luck.
[UK]J. Barlow Burden of Proof 167: You were class, man. I had respect for you.
[US]E. Torres Carlito’s Way 18: I was less into being a thug and more like a class guy.
[US]J. Ellroy Brown’s Requiem 118: I knew right off the bat that this was a class place by T.J. standards.
[Ire]E. Mac Thomáis Janey Mack, Me Shirt is Black 21: No, this mot was class and so was her mother.
[Ire]P. Howard The Joy (2015) [ebook] This bird is class.
[Aus](con. 1964-65) B. Thorpe Sex and Thugs and Rock ’n’ Roll 15: This was a hot club [...] The girls were class, the drinks were thick, and the vibe was definitely happening.
[UK]N. Barlay Hooky Gear 238: Uncles in there now, puttin on a class voice.

In phrases

no class (adj.)

styleless, socially inept, unable to fulfil the group norms.

[UK] ‘’Arry and the [...] Lady Cyclists’ in Punch 15 June 285/2: Poor Lil! She’s no clarss, not comparative.
[UK]‘Doss Chiderdoss’ ‘An Ungrateful “Missis”’ Sporting Times 25 Aug. 1/4: I am told that I’m lazy, and also no class.
[UK]Marvel III:57 29: Serves me right for picking up with no-class chaps like him!
[US]H.S. Thompson letter 25 Sept. in Proud Highway (1997) 585: It was a completely ‘no class’ piece of action.
[UK]J. Cameron It Was An Accident 38: Never liked supping on the street, no class.