Green’s Dictionary of Slang

(orig. US) a fair chance.

1908		H. Green Maison De Shine 209: I’m a reasonable feller, an’ have been. All I ast is an even break.
1914		Day Book (Chicago) 18 Apr. 28/1: The team must chirk up in order to get an even break.
1928		M.C. Sharpe Chicago May (1929) 29: He told me, however, that he would see that I got an even break if I treated him right.
1936		J. Curtis Gilt Kid 101: If he could get one of these lays weighed up properly there would be an even break of getting a good night’s wages.
1940		F. Bason Diary I (1950) 96: I’d write all his stuff for him if only he’d give me an even break.
1949		Monteleone Criminal Sl. (rev. edn).