This GS 160 is for sale right now on Ebay in Colorado. The scooter looks very correct, and it is clear that a high quality restoration was performed. You just don't see too many of the first series GS 160's around. The main cosmetic difference between the first and the second series was the location of the glovebox. On the first series, the glovebox was in the frame, with a small access hatch located just behind the seat. The glovebox was quite small, and because of the location, blocked the use of a rear carrier. The second series had the glovebox located behind the legshields. The second series glovebox was much larger than the first series, and hence, much more practical. The other main cosmetic difference is that the first series had a round rear frame, and the second series had a square rear frame. For that reason, you sometimes hear the first series GS referred to as the "round-tail GS".
The "buy it now" on this one is pretty high, at $10,000 USD. I have not seen one of these sell for that kind of money before. I'm guessing that he would find a buyer if the price was in the $5-6,000 range.