Yep, have all that stuff too. The metal plate wasn't an MB specific thing. You'll often hear about them on shows like Barrett Jackson, etc.

They were used by mechanics/dealerships, etc., to ensure proper parts, chassis codes, diagnosis, etc. were used for service/repairs/maintenance/parts ordering/etc.

Keep it with the car. Keep the car too.

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1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)