A lot of times when I get a scratch on a bag, and when it is of good leather like Dior, etc, rub your finger deep into the scratch over and over again and usually the leather repairs itself. No nails, just the pad of your finger and some pressure over and over again. Its kind of like burnising something.
Usually, that's how I can tell if a bag is made of the type of leather that I would want to own. If I can rub out a scratch, where the leather starts to look like itself again, then I know it is a good quality leather for me.