We should rename all those P601 to 601 chassi P601 as Ralph sugested http://www.imcdb.org/vehicle.php?id=70922

Is it sure?
What about the P50? And the P601 Universal/Kombi/Kübel?

That seems correct, after looking through these: http://www.mclellansautomotive.com/sales-lit/bymake/trabant/index.shtml

P is never used as pre-fix in the sales literature above.

Yes that's true "601" is correct, at the beginning, in "my" first movie here, I've added one under this name (601), but someone has renamed it. and next cars I've named P601 like others on the site.
So all 601 should be listed without "P" (Universals etc. also), P50 is ok.

Done.