Howdy: The word "Southampton" meant that the car was a four door hardtop as opposed to a pillared sedan. All of this came about because the first four door hardtops were introduced by GM in midyear of 1955, with the Buick & Olds. And they were called Buick Century "Riviera" or Special "Riviera" or Olds 98 "Holiday" or Super 88 "Holiday" so Chrysler followed suit and brought out their own language "Southampton" which meant that it was a more expensive car and more fabulous car than just a pillared sedan in all of the series offered by Imperial during those fabulous years; the likes of which we will never see again! Doug/Los Angeles, California