Green’s Dictionary of Slang

(US) admirable, excellent, acceptable.

1893		J. Hawthorne Confessions of Convict 143: She has buncoed many millionaires. She’s silk! She’s one of the best ‘con-women’ in the world.
1926		(ref. to 1880s) ‘Coonjiner’ in AS I:6 Mar. 362: Wuzent Ah happy? Bushel an’ a peck, / Feelin’ lak silk – mighty fine.
1927		D. Hammett ‘The Big Knockover’ Story Omnibus (1966) 305: All silk, so far.
1933		N. Algren ‘So Help Me’ in Texas Stories (1995) 18: He ain’t goin’ to hop nothin’ but blind baggage on a silk manifest.
1943		R. Chandler Lady in the Lake (1952) 57: What Muriel did was all silk with me.
1997		Fraser & Meadows TwentyFourSeven [film script] (1998) 22: Giz the ball and I’ll show you my silky skills.