Thanks for the help already guys!
Restoring will take long though, so we aren't sure if we want to put our time / money in it. Is there someone out there who can value this car (which has knowledge of it ofcourse)?
FCA wasn't able to provide input (asked the contact person if he has ever seen something like this, didn't really answer), so it's great to receive some answers here!
Well, the owner says it is a Diplomat and so does the official booklet of customs (and governement, CoC) that we have. We have all the papers that belonged to this car, which gave us some small hints to search for.
The dashboard has a "FireFlite" emblem so we know it shares some parts with that.
If someone wants some more pictures, let me know, I have a couple more!