So in the episode "Tomorrow is Yesterday", regarding his ship, Kirk tells Christopher that "there are only twelve like it in the United Earth Space Probe Agency". Now we have to take Kirk's comments with a grain of salt since he's trying to deal with a 20th century human, but if he means Federation Constitution class starships, which would they be? Here are the ones shown in TOS and TOS remastered: 1. U.S.S. Enterprise (NCC-1701) ("The Cage" et al.) 2. U.S.S. Constellation (NCC-1017) ("The Doomsday Machine") 3. U.S.S. Intrepid (NCC-1631) ("The Immunity Syndrome") 4. U.S.S. Potemkin (NCC-1657) ("The Ultimate Computer") 5. U.S.S. Excalibur (NCC-1664) ("The Ultimate Computer") 6. U.S.S. Exeter (NCC-1672) ("The Omega Glory") 7. U.S.S. Hood (NCC-1703) ("The Ultimate Computer") 8. U.S.S. Lexington (NCC-1709) ("The Ultimate Computer") 9. U.S.S. Defiant (NCC-1764) ("The Tholian Web") 10. 11. 12. So which other 3 Constitution class starships do we pick from non-canon works to fill in the gap?