The only detail that catches my eye is the tank and Suzuki font. When compared to the stockers, the works bikes of this era did have the font in a slightly lower position on the side of the tank...the font was also slightly larger. This matches a works tank.
So, it MIGHT have a works tank. But it also might simply be a repainted stocker. In any case, there are still far too many production parts on this model. And the fact that he won't let anyone see it in advance smells of rat's play.
But for fun, you should read through the question and answer session on the listing! Good banter.