Nickel Curve (1928)

He [Artie Reinhart] has a slow, teasing curve and looks as though he hasn’t got enough stuff to fool a semi-pro club. Yet game after game, inning after inning, Reinhart get his so-called ‘nickel curve’ curve up to the plate and nobody seems able to do anything with it.Brooklyn Times, July 26, 1928, p28

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1945. “Keep throwing that nickel curve” (Council Bluffs [Iowa] Nonpareil, Sept. 9; Merritt Clifton).