Ralph, Jonny B, Gary, Rob & DM, thanks again for all your advice. I managed to take up contact with Tom Hansen and he has been very helpful in sorting my issue with the data card (thanks Gary). I will now send a PM with the complete card to DM.
Since my last correspondence I have spoken with several more Mercedes and Tyre dealers on the subject of the additional letters in Box 19. I regret none have been able to provide a definitive answer although the majority agreed that it was likely information related to the type of tyres that were delivered with the vehicle. Rather than speed rating one suggested that given these vehicles were destined for different world markets that it might be related to the climate and typical road conditions of where the vehicle was destined.
As to the large “1”, “2” & “3” printed on the data cards. Again not many of the dealers or the people I contacted at the Classic Centre in Stuttgart seem to have a lot of knowledge on this subject. An older specialist I came across seems to recall that all vehicles from this period should have been delivered to the customer with at least two (2) Data cards. One card marked “1” which was the original, contained the key codes and description of the codes printed on the back. The “1” card was to be removed from the vehicle/log books and kept in a secure place (at home) by the customer. As Ralph suggested “2” & “3” were copies and typically did not have information on the reverse nor key codes. The “2” copy was typically kept with the manuals etc., in the vehicle. The specialist thought that the “3” data card was scanned and stored on microfiche at Mercedes and the card itself may or may not have been retained by the dealer network. He said that during the production of the 230SL, 250SL & 280SL the format of the data card changed quite a bit (as outlined in the Technical Manual) and that dealers may not have always followed the correct procedures with respect to cards.
As to the red/pink cards that Ralph has he did not know but suggested that he may have been provided with these additional cards as he collected the vehicle directly from the factory rather than via a dealer.
I would be very happy to hear from anyone who can verify any of the above. Thanks Surfer.