Princeton history graduate student Benjamin Schmidt explores changes in language through TV anachronisms. In Schmidt’s most recent analysis, he examines Megan’s use of “callback” in the last episode of Mad Men. Above is the ratio of modern use to period use. Notice callback sticking out in the top left.
The big one from the charts: Megan gets “a callback for” an audition. This is, the data says, a candidate for the worst anachronism of the season. The word “callback” is about 100x more common by the 1990s, and “callback for” is even worse. The OED doesn’t have any examples of a theater-oriented use of “callback” until the 1970s; although I bet one could find some examples somewhere earlier in the New York theater scene, that may not save it. It wouldn’t really suite Megan’s generally dilettantish attitude towards the theater, or the office staff’s lack of knowledge of it, for them to be so au courant. “call-back” and “call back” don’t seem much more likely.
Other anachronisms include the use of “pay phone” and a frequent use of “on the phone with” which didn’t peak until the 1970s.