We know a song about this... dont we children... and todays letter is 'Q'
If you get caught out.
At least the chap was decent enough to tell you about it before you parted with your hard earned.
As has been said.. its worth what its worth... whatever you want to pay for it.
Some people will say its a re-shelled RS, others will say its an XR with a turbo motor in it....
Is it cheap ?
If it is, buy it, if it all goes wrong then break it.
If its not, walk away, there are still good genuine cars out there.