This is the infamous "rod bender" diesel engine, there's more or less about a 50% chance that this example could be a bad one. Do a search for "rod bender". It COULD be all right, but I wouldn't chance it.
It's also way overpriced for what it is. Perhaps you'd be better served by looking at the earlier models, like an 84-87 SD or SDL sedan, without the trap oxider problem, and rust free. That's just my opinion.
Although it is written for gas powered W126 coupes, the buyers guide at
www.mbcoupes.com is worth a look, for the tips.
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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...
1995 E 420, 170k "The Red Plum" (sold)
2015 BMW 535i xdrive awd
Stage 1 DINAN, 6k, <----364 hp
1967 Mercury Cougar, 49k
2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive

(sold)