That Rothmans one also looks like it's been stored under a tarp in a carpark!!

As others have said you really need to know what you're buying. When I bought my first NSR I went for a cheap <£1000 one so that I knew I couldn't be disappointed! Predictably I found the bores and pistons ruined and various other things. Doing the top-end alone with new parts and re-coated cylinders is the best part of a grand. So if you're paying £6000+ then you want to be confident it's going to have a lot of life in it. However it depends if you want to buy one good to ride or have a project - every day my project bike seems to get further from completion!

One way to know you're getting a good one is to examine it as thoroughly as you can, the other way is - as Andy advises - to use your judgement on how genuine the seller is. I bought an MC21SP off a known member on here and I had absolutely no doubt that it was a good buy - you just have to use your intuition, because unless you're buying one in bits how do you know if it's been recently seized/abused?