I have one with my U.S.-spec 1967 230SL, manufactured in 1966. But the interesting thing about mine is it is not for my car, but for someone else's! The chassis number is close but doesn't match. My guess is the dealer somehow got them mixed up. But that's just a guess. Very unfortunate, because it shows the original buyer's name (well, a business).
I believe these tags were used by the dealer service departments when you brought your car in, and were used to stamp the invoice, sort of like the old credit card machines.
Brian