The rear seat in the Mercedes W123 consists of two pieces: the seat base and the seat back. The seat base is the lower part of the seat you sit on. The seat mounts to the floor pan. The seat back is the part of the seat your back rests against. This part of the seat clips onto the boot frame. If you need to remove the seat to gain access to the fuel pump or you want to complete a vehicle restoration on the W123, you should find that the process is straightforward.
Remove the bolts that secure the seat base to the floor pan with a socket and ratchet. The bolts are between the centre cut-out in the seat where the seat belt fasteners come out of the centre of the seat. Remove the bolts with a socket and ratchet.
Grab the front of the seat and work your fingers between the floor pan and the bottom of the seat. Pull up to force the clamps out of the floor pan and pull the seat forward to separate it from the seat back.
Push the seat belt fasteners from between the two seat panels and remove the lower seat from the Mercedes.
Grab the bottom of the seat back where the seat was joined with the seat base. Pull out on the bottom of the seat to remove the clips from the boot frame. Keep pulling until the entire seat is free from the boot frame and remove the seat back from the Mercedes.