137th Gebirg wrote:
Granted, Enterprise's NX-01 and Columbia's NX-02 somewhat muddies that argument, but it could be counter-argued that that's what they did for a while in the 22nd century, and went to an NCC-??00 style in the early 23rd century for a limited period of time.
The 22nd century Enterprise was an NX class starship, and the first one in the fleet, hence NX-01. The Columbia was the second, and thus NX-02.