A couple of the photos are promising (others are not) but, unless I was able to actually see the coin, I'd want some independent verification of it being a proof. Even then, I'd probably want a second opinion. How about offering £1,500 on the basis of it being slabbed as a proof by CGS? Or getting an independent report by, say, Mark Rasmussen? For a genuine proof, that's a fair price though. As an aside, for a £1,500 (asking) coin its getting some rough handling by these so called experts!