Get the shelf out use as a pattern. 1/8 mdf, jigsaw, matching vinyl, contact adhesive and bingo a new one!

Yes, there is a board behind the seat. Nissan calls it the "parcel shelf".
It is stained and warped.

Then there is the black trim under the window, visible in this photo.

Great job dude! thats a handy tip for all

pretty cool how the backs are the same
shouldnt there be a board of some description under the window?

Now what can I do about the trim under the back window?

I'm so enthused about this. Finally got 1/2 a good seat. Suprise: B210 sedan rear seat back is identical to B110.




Next I need to find a good seat cushion. The old seats were recovered in ugly gray vinyl. They were stuffed with foam and so had lost all shape as you can see on the bottom.