CHICAGO (CBS)— Providing a bit of a peek into the private life of Hugh Hefner, the Playboy boss’ “Little Black Book” is going on exhibit at the Chicago History Museum.

The book, along with one of those “While You Were Away” message notes found inside, will be displayed as part of the museum’s “Unexpected Chicago” exhibit on Friday.

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According to the museum, Hef used the book way back in the 1950s “while his celebrity was on the rise, building a world empire of fantasy and desire where readers could escape their troubles by getting caught in the teasing gaze of the centerfold-of-the-month.”

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Hefner, who left Chicago for Los Angeles years ago, used the book to jot down notes about women he met as he was beginning to build the Playboy empire.

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Hefner, who turned 86 last month, founded Playboy in 1953–with the very first issue famously portraying Marilyn Monroe on the cover.