Green’s Dictionary of Slang

1. first-rate whisky, the genuine thing as opposed to the ‘bathtub’ or ‘rotgut’ versions producing during Prohibition.

1931		‘Und. “Lingo” Brought Up-to-Date’ L.A. Times 8 Nov. K16: QUILL: Genuine whisky.
1949		Monteleone Criminal Sl. (rev. edn).

2. first-rate opium.

1935

A.J. Pollock Und. Speaks n.p.: Quill, choicest grade opium.