@davidships, pha and geoff.thank you very much for your help.you are the best.now i can put the right name in my photobook.

She was replaced by the KÖNIGSWINTER IV, built in 1996.
http://www.faehre-koenigswinter.de

@ davidships: Sorry. It was my typing mistake. Yes, ship was built 1960 by Oberwinterer Schiffswerft Clausen. Name has been inserted by admin. Regards Peter

Sorry about my doubts!
But built in 1960, not 1970
Apparently purchased 9/1998 by Treibgut Veranstaltungen GmbH, Cologne/Köln, and converted to an "event ship". 300m² hall. Looks as if that business failed. For sale in 2012 at Duisburg.
http://www.binnenschifferforum.de/forum/showthread.php?47637-K

Presumably name is still TREIBGUT; appropriate now, since it means flotsam.

Mistery solved. Thanks to Wilhelm Langes of fjordfaehren.de. (first address for all european inland ferries!) Ship was the original rhine-ferry "KÖNIGSWINTER III". Built 1970 by Oberwinterer Schiffswerft Clausen. Out of service since 1999. Made Rhine ferry service between the City of Königswinter and Mehlem, district of the City of Bonn-Bad Godesberg. Old postcard: http://fs1.directupload.net/images/150727/qfiespf3.jpg
Rebuilt in Duisburg into the event- and party-ship "TREIBGUT". Actually laid up at Duisburg. Original data: LxBxD 40 m x 15 m x 1,10 m - 500 passengers, 35 cars, 4 x 150 hp Daimler-Benz Diesel OM 326 on Schottel SRP 100. Regards Peter

I wouldn't have thought ever a ferry - looks like a standard pontoon barge with an added superstructure - office, club or what-have-you.