That's why VINs make a decent natural key, because they do have a check digit. Plus they're not opaque: if you look up the VIN and the make/model/year is compl

That's why VINs make a decent natural key, because they do have a check digit. Plus they're not opaque: if you look up the VIN and the make/model/year is completely different than the car in front of you, you know you either have the wrong VIN or the wrong car.