whunter nailed it, but the easiest way to tell the model would've been to just look at the 3 digits following the 126 in the VIN. The 3 digits following the chassis code are the model code. Ex: 126120, 120 = 300SD, 126022, 022 = 280SE.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.