Does someone know this bus?

[tggwtb]

Hello,
I know it's very unlikely, but does maybe someone know this bus?
facts I know:
- delievered to NY in autumn 1964
- sometimes in the 90's in alabama
- at last in Califonia (see registration-plate)
- in 2006 gone back to germany
- for ten years in the garage of the pre-owner, who tried to restore and modifing or something
- since christmas 2016 at my place

When I found it, there was no more paint, it was striped down and very incomplete, no backseats, partition panel and dashboard cutted.

VIN 255020xxx

So, have someone an idea what happend in the fourty years at USA?
I would be very happy about old pictures or something else.

Thanks