I know many fans have questioned the "0" in front of the Kelvin's registry, but perhaps it can make sense in a real world manner. As an airplane enthusiast I was reminded of the Navy and Air Force practice of placing a 0 before the registration of any airplane in the fleet that was older than 10 years. Perhaps this might explain the Kelvin's registration-early Starfleet practice adopted the same method and it was later dropped by the time the Enterprise 1701 had reached its ten year mark (which at least according to TOS was rare for a ship to do). Does this make sense to anyone?