crow mcgee, adj. — Green’s Dictionary of Slang

crow mcgee adj.

[ety. unknown; ? joc. reversal of real McCoy, the n.]

(US prison) no good, unreal, false.

1935		A.J. Pollock Und. Speaks 27/2: Crow McGee, not genuine, imitation.
1936		San Quentin Bulletin in L.A. Times 6 May 7: CROW McGEE, no good, not the real stuff.
c.2003		Holoban on University of Missouri Amer. Studies 🌐 McCoy: Genuine (opposed to Crow McGee).