Certainly a very, very interesting rug. Although, I do not belive this is half the age the seller states it is. From what I can see, (and the pictures are not great) especially regarding the color and design execution, I would guess this is an Isphan or Tabriz - and I'm leaning more towards the Tabriz. It was probably made sometime in the 50's to mid 70's. I say this because of the intensity and tone of the colors used, although it could even be newer. Some of these more unusual designs were meant for the markets closer to the areas the rugs were woven. How much is he asking, what is the KPSI? Great post by the way, really interesting rug.
If you requested photos of the reverse of this rug, and a close up of the corner with the fringe of the rug, I would be able to make a much better determination for you. As of right now, I'm not entirely convinced it is what he says it is.