Susie tells Midge she has a gig as a headliner in Zagreb, Croatia. She repeatedly says, "Croatia". In 1960, Croatia was a region of Yugoslavia, not an independent nation that would be referenced in entertainment circles.
Croatia did not exist as a country until 1991. At the time of this episode it was part of Yugoslavia.
The phrase "bad hair day," said by Midge in her stand-up routine, had not entered the vernacular in 1960. The saying dates from the late 1980s or early 1990s.
A stripper tells Midge she will give her the number to make contact for a Women for Kennedy fundraiser that needs a female comedian and begins writing the number on a piece of paper. Midge leaves with her friend before being given the paper with the number.