The fact that it has a US VIN suggests to me that it was converted (hacked?) in the US and therefore is worth less than a comparable as-delivered 560SEL.

If the conversion can be traced to Binz or some renowned(sp?) coachworks, then you might have something. Otherwise it might as well serve the rest of its days as an airport limo.

And Aaron says...

Sixto
91 300SE
87 300SDL
83 300SD