How so? It just adds another block of numbers to the mix: say, 1700-17XX for ships like the Enterprise
, 18YY-18ZZ for ships like the Reliant
, and 1000-10AA for ships like the Constellation
That the Enterprise
and the Constellation
look alike doesn't need to mean much. So do, say, the Spruance
classes of USN ships, but the last has registries in a completely different block from the others.
The thing is, ships with 18XX registries apparently already existed back in TOS "Court Martial", so a refitted Enterprise
might be more modern than an unrefitted specimen of the 18XX class of ships. Or the refitting in the 2270s might have eliminated any differences in modernity between the classes.
What Khan's ship has over Kirk's is never specified in dialogue until after Kirk's ship suffers damage, gives Khan's ship some, and both sides implement hasty repairs, with different priorities. It's only then, after a very thorough shuffling of the cards, that Khan is stated to "out-run and out-gun" Kirk. And Khan did get more shots in than Kirk did...