Green’s Dictionary of Slang

1. a bookmaker.

1902		Daily Mail 17 Nov. 6, i: What they shudderingly designate a skinner was enjoyed by the majority of the layers when old Fairyfield credited Mr. George Edwardes with the Belper Selling Plate [F&H].
1910		‘Doss Chiderdoss’ ‘A Derby Bet’ Sporting Times 28 May 1/3: I’ll bet that the layer was Conkles, renowned for his many-hued ties.
1913		Sun (NY) 27 July 40/1: Things are pretty tough. [...] They’re running out on the books at Belmont Park so fast that a layer won’t let anybody go on the nut for more than one iron man.
1966		J. Holledge Great Aust. Gamble 67: Gone forever are the leather-lunged layers like Joe Thompson, Humphry Oxenham [...] and Andy Kerr.

2. (US Und.) one who passes bad cheques.

1914		Wash. Post 11 Nov. Miscellany 3/6: In certain circles a bad cheque is a ‘scratch,’ the maker of which is the ‘scratcher’ and the vendor is the ‘layer.’.
1929		Hostetter & Beesley It’s a Racket! 231: layer — A forger’s accomplice; a check or note forger.

3. (US Und.) a short-change artist.

1928

J. O’Connor Broadway Racketeers 253: Note Layer — A short change artist.

4. (US) a currency note.

1933		C. Himes ‘Prison Mass’ in Coll. Stories (1990) 164: He had put the bee on Jean for some ‘layers’.
1944		C. Himes ‘Let Me at the Enemy’ in Coll. Stories (1990) 38: Cats say they’re goin’ East — slip up there an’ make them layers.