you anorak
What I can tell you is that I?ve seen this car at the ring several times already (assuming it?s the same one, it?s hard to tell from a webcam picture and without being a jag-anorak). It was there during the tourist sessions, which implies that it has to be road legal somewhere, although I don?t remember what country it was registered in. It also has semi-slick tires, and unlike many of the other nice cars that just show up at the parking lot for show and shine, this one actually goes round, so I?m thinking it?s probably not a 2 million dollar original...
edit: I found this, it doesn?t look like it has semislicks, but feel free to go nuts