Somethings just don't look quite right to me on that bike.
No front turn signals.
Rear backrest is not straight and appears to have aftermarket upholstery.
In the Auction house photos it shows an aftermarket windscreen, that was available back then. Could be a SlipStreamer, or something of that type. But it is removed in the Fleabay add.
Also, from what I remember from that era, the raised lettering on the gauge pod would have been white. I may be incorrect.
There appears to be something not quite right with the odometer. Those numbers do not line up quite right to indicate the low miliage he claims. I am almost thinking that the speedo may have been tampered with. It looks like it is turning of 55555 miles on the odometer and 130 on the trip meter.
The grips are definitely incorrect.
The serial number given on Fleabay comes up as
04/1974 2476 R90/6 USA
Production Code: 0273
After all is said and done, it is still just a 1975 R90/6. Nothing really special, as far as I am concerned. I always felt the /6 bikes were just interim ones that were waiting for the /7s to come out. I would rather either a /5 or /7. This one is only worth maybe $3000 if in excellent running condition. If it has been sitting for as long as he says and not ridden, maybe $1500.