For what it’s worth, other "Registries" I have cars registered on all use VIN numbers [the last 4 digits].
If one wants to get very detailed; VIN, Chassis, Body Frame, and Engine numbers are all part of each M3W’s pedigree.
Why is that the last four numbers of the VIN start with "2"? For example, mine is the 931st M3W to leave the factory and its VIN ends in "2931". Presumably the 1000th (assuming there is only one of them) has the VIN "3000".