A single date like that on 243 should mean that that description is still valid - i.e. sport seats. This was done by the Russian MB Club and some of it may involve human intervention, interpretation plus language translation. For example number 261, elimination of the V12 model designation dating to 1973, would appear to be nonsense. That said it's a great site. For more factory like precision you may want to get the production data card from the factory or the VMI from a dealer.