Green’s Dictionary of Slang

(US) of currency notes, large-denomination.

1896		F. Hutcheson Barkeep Stories 137: ‘I got de goods, d’ you understan’? But it’s all in coarse currency an’ I’m kinder scared t’ change it’.
1937		D. Runyon ‘Blood Pressure’ in Guys & Dolls (2008) [ebook] They all have big coarse G notes in their hands which they are tossing back and forth as if these G notes are nothing but pieces of waste paper.