Seat question

[Lee72]

Working on a new to me 68 c10. Came
With and extra bench seat. One in the truck was pretty torn up on driver side. Extra seat was not. Put it in just so I wasn’t dealing with all the insides coming out while I’m workin on it. Realized after I put the other one in is that it is fixed and doesn’t fold forward. It bolted right in with no problems. What could it be out of? I assume something with four doors like a suburban.