Are rear folding seats an option?

I have a '91 525i, and can't locate the "loop" to pull the rear seat out to fold it down for extra storage (as described in the owner's manual). Then I got to wondering, maybe all models don't come with this option. If they do, is there a trick to get the seat to fold? Thanks for your time!

My 1990 535i doesn't have folding rear seats. And in 1997, 1998, and even later, folding rear seats were a $475 option (which I think required the $3,450 Premium Package).