 DATE: When Truman Capote is speaking on the telephone in one scene,  the handset is clearly connected by an RJ22, four pin connector.  These "Registered Jacks" were not invented until the 1970s and the  scene takes place in the early 1960s. Also, when he is speaking on  the phone with William Shawn in 1959 after first reading about the  Clutter murders, the phones dial is plastic. Rotary phones then had  metal dials.