In California the month/year of maufacture and the month/year when first sold are on my DMV vehicle registration card. So I know, for instance, my 1984 300SD was made in November, 1983 and first sold in Feb., 1984. Might be worth a look FWIW.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)