[lucas_membrane]

VIN is a good example of how this stuff gets pretty crazy. The standards define it so as to be unique, but only unique within defined n year ranges of model years (VIN identifies vehicles), where n depends, however, on the vehicle type, which can be determined from some specific sub-fields of the VIN. So, multiple vehicles may be on the road with the same VIN if at least one has survived more than n model years (which map flexibly and only approximately to ordinary calendar time). In addition, sometimes a manufacturing error produces non-identical vehicles with the same VIN because of blunder by human, machine, or both in concert. These scenarios are resolved by IT means similar to the method used by Mark Twain and his parents to avoid confusion between him and his mythical twin brother.