Bob, I think most of the more serious pollution control equipment came on for the 280, (mid year 1969 11948), some came in when the big switch was made mid run on the 250SL (with all the other changes at 2980). For the early cars, other than the most basic kind of stuff, PCV and the little fume collector pot inside the right rear fender, there is not much to speak of. Two issues back on Pagoda Notes (the edition that has the information on literature has a photo (from the model brochure) of the engine bay.