?tis the prize for golding the top gear challenges. I always thought it was prize only, but I saw a thread on here where somebody claimed to have bought it from the UCD
As for rarity, since I started collecting cars, there are still 2 that elude me in the UCD/OCD and that's:
Pescarolo-Courage - Judd GV5 Race Car '04
Clio Renault Sport Trophy Race Car '00
So for me, these cars are rare, and I check the garages often.
I thought the Proto X2010 might have been in my grasp after golding Monza, but then I tried Nurb GP and reality bit hard.
Then there's the Chromeline and Stealth cars, which aren't so much rare as excusive. I keep getting this crazy idea of buying a signature ed if you can still get them new, just for the cars.
The Nissan from the OP - I have 2, bought one, then won the other for licenses, I think.