First choice in doing a correct restoration should be single stage, but there are many reasons a shop or owner may choose to go with BC/CC. On a T-bred/Premiere car, it's more critical that the paint system be single stage, but otherwise, if it appears correct as Bob P mentioned, I don't see any issues in Concours. We're not going to ask owners to rub an area of paint to see if color comes up, we will simply judge them as presented. The only time BC/CC becomes a big issue is when there has been extensive 'cut and buff', which removes all orange peel.