Green’s Dictionary of Slang

the female breasts; usu. qualified by an adj., e.g. big ones/nice ones.

1977		(con. 1949) J.G. Dunne True Confessions (1979) 66: Nice ones, Jeez. I bet she had nice ones. Pointy, you know what I mean.
1986		L. Heinemann Paco’s Story (1987) 62: A tall, healthy-looking woman with a large head of hair [...] and ‘a nice set of big ones,’ the rednecks will tell you.