Robert Comsol wrote:
P.S. I'm aware of the concept of changed premises and intentions. Is there evidence that the TOS producers changed the "Starship Class" concept during the original series?
Maybe not during TOS, because obviously they had bigger fish to fry than the minutiae of ship classes. But we do have the technical manual from the mid-70's, which elements of made it into TMP and that publication listed the Enterprise as being a Constitution-class starship. And the publication, at least at one point, had Roddenberry's blessing.
Plus, the second episode of TNG uses Constitution-class when describing the Enterprise. Roddenberry was also in charge of the production.