Walnut was standard on all 6.9 vehicles.
However, as we all know, MB would oblige even if you wanted plain back (as long as you paid for the inconvenience)
Michel, walnut only became standard probably in 1978 (or 1977). However, early models actually came without timber embellishments. E.g.,early models had plain heater and gearbox console vinyl covers as on some of the other LESSER models. Regards Styria