Each chassis has 6 numbers. the first three are common to all body styles covering a number of years. the w126 ran from 1981 to1 991 I think. After the first three numbers, and following a dot are three more. These are specific to the year. Mine is w126.035 for a 1986 420SEL. I don't know if there is a chart anywhere that has all the chasis numbers and the year they match to or not.