Pawel,
I called Brian Peters at Motoringinvestments and his "holy grail" car has MB-tex. The insert shown in the photo has a heat-embossed rim around it and he believes had once a foam backing that crumbled away. Unfortunately, he has never seen a leather insert, but also has never seen one that was glued to the wood. So foam backing may be correct for vinyl.
Jordan,
it is very likely that 230SL cars never had a carpet insert. The spare parts list (10126) shows one p/n for the insert: 113 840 01 75, and that one is vinyl.
The international spare parts list for 250SL/280SL (10202) also shows this p/n. But Dave Gallon told me that the US spare parts list (10808) shows that p/n 113 840 01 75 was replaced by 113 840 06 75 which is the carpet piece. He does not know when this happened but most likely in 1970.
Then there is a third p/n in the US list: 113 841 05 90; we believe that this could be the leather part. Importantly it was also replaced later by the xxx06 75 carpet part.
When I restored my 230SL and replaced MB-Tex with leather and installed new carpets, the carpet kit included a piece for the tray and since the original vinyl strip had shrunk so much I used the carpet piece. Totally unoriginal, as Achim would say, but it looks a lot better than the wrinkled, shrunk and discolored vinyl strip that would not stay in place.
