Quite possible they're 107 or 126 seats...up to '85.
You can lift an edge of the material under the seat to determine if it's leather or MB tex (Vinyl).
Also, if you see fine, uneven "veins" in the bolster they're most likely leather.
Is there an armrest attached to the side of the driver seat that pivots up and down?
A better place to post is here:
http://www.mercedesshop.com/shopforum/forumdisplay.php3?f=1
Since I'm registered I can post for you if you'd like.