Green’s Dictionary of Slang

ticket n.2

[play on tit n.2 (1)]

(US) in pl., the female breasts.

[US]J. Olsen Secret of Fire Five 49: The lady [...] lets out a shriek and lifts one kneecap over her private parts and her arms over her big tickets.
D. Jenkins Slim & None 3: [S]he was wearing the minimum legal requirement of a white knit top. This helped her display two tickets that would easily gain her admittance to the hospitality tent.