The owner knows the value. Here is an idea find a perfect W126 for sale around you and take a look at it. The W126 is really a nice car when it is fully sorted. I am just getting to that point with mine, a 560 or 420 would probably be an extremly quit car inside, they handle awsome(for their size) not to mention the brakes. Exhuast's are not to bad probably well under $1k for a complete new one. (I think). Compared to my Toyota or my moms Olds the Mercedes feels alive, it is truly a joy to drive.

This statement I have learned the hard way is extremly true, all of my future purchase's will be guided by it:
"the most expensive Mercedes is a cheap one" Buy the best one you can afford with a complete service history. With one or two owners, no accidents, stories etc. Then have a good mechanic go threw it front to back top to bottom.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200