Green’s Dictionary of Slang

(US) at an angle; also adj.

1958		I. Blassinghame Dakota Cowboys (1964) 130: set my hat at an ace-deuce angle.
1965		H. Williamson Hustler 70: There’s vomit all over the bed, all in my hat, and that’s sittin’ ace-deuce [f.n.] on my head! [f.n. Low and to one side].
1971		D. Goines Dopefiend (1991) 182: [He] set the hat ace-deuce across his head.
1972		O. Hawkins Ghetto Sketches 17: Sweet Peeter D. cocks his lid ace-deuce.
1980		E. Folb Runnin’ Down Some Lines 227: ace-deuce to the side 1. At an angle. 2. To the side.
2012		‘Dutch’ ? (Pronounced Que) [ebook] [...] putting a white fedora with a black band on his head and cocked it ace-deuce.