That looks like the German Polyroof conversion. Very high quality roof but expensive. WWW.polyroof.de Visited their factory and was very impressed with their care and attention to detail, was considering having Cali converted but chose the Westfalia joker instead.
I'll agree with the theory that the roof was from Polyroof as I believe they make the roof for the SWB Cali high top that we never (almost) see here in the UK. There was one from Wolfsburg or Hanover at Vanfest some years ago.
The one pictured was believed to be a prototype from the factory and the WOB plates would support that.