Green’s Dictionary of Slang

smooth article n.

also smoothie

a sophisticated, smart person, both mentally and physically.

[US]O.O. McIntyre New York Day by Day 15 Sept. [synd. col.] The gate crasher is proud of his work [...] and is regarded as a smooth article.
[US]Howsley Argot: Dict. of Und. Sl. 46: smooth article —a nicely dressed, attractive female; a ‘slicker’.
[UK]Indep. on Sun. Culture 15 Aug. 5: Lovable rogue, irresistable smoothie, gentlemanly cad.