the only surviving Kohlruss-Bus found in 2014 in the above image, you can read the story in German language here: http://www.bullibar.eu/der-kohlruss-samba-nur-einer-hat-uberlebt.html or in English here: https://www.thesamba.com/vw/forum/viewtopic.php?t=649306
Kohlruss is mostly known for his barndoor deluxe buses. He ordered panels from Wolfsburg factory – sometimes with sunroof, sometimes without – and built very special buses.
The most significant feature of such buses were 2 special built windows above the dashboard in the roof of the driver cabin. Some other characteristics were the long sliding windows on the sides – they enabled a better panorama view and an improved air supply.