But it is worth noting that the designation was not carried forward into the second season writer's guide. So, while it was later picked up by fans and licensed works and ultimately by the franchise itself, it is very much possible that the idea was nixed by the TOS production staff. Matt Jefferies, at least, famously thought in the beginning that the Enterprise was the "first bird."-2. It's scripted in "Space Seed" that Khan was looking at Constitution-class schematics [https://collectingtrek.ca/2020/08/13/enterprise-is-not-constitution-class/].
-1. It's on a diagram Scotty is looking at in "The Trouble with Tribbles" [ibid., http://trekplace.com/article10.html].