And we know there are only twelve like it in our possession.
And from this it is generally taken that there are only twelve Constitution class ships overall. But isn't it possible that there are variants within
the class? The Enterprise in The Menagerie had a number of physical differences to that in the mainseries, as well as a much smaller crew. Perhaps the ' only twelve like her' description was of a specific configuration, an upgrade that only a few Connies had received?