I'd be curious to know why the seller believes this to be the 1st CS built.
It seems to be the owner not the seller who is claiming this and the mileage. Seems to be a consignment sale.
The mileage is printed on the show board.
Assuming the car isn't driven much if you put the mileage on your show board or you have to keep updating it.
Interesting paint job on the window washer reservoir.
Not original but an interesting touch.