There was only 1 Cabriolet factory fitted with rear seats – Lady Diana’s.
However, Jaguar dealers provided to their customers the option of having rear seats. These were carried out locally, utilising XJ-S Coupe seats.
You’ll see lots of different variations of rear seats, depending on what the dealers could obtain as much as anything. There will also be some that the owners of the car at some point in its life retro fitted rear seats.