The "Phase II" refit of a Constitution-class Federation Starship. TOS was set from ca 2266 to TMP era refit would have been ca Average ship service-life was only 5 years, so a major refit after about 5 or 6 years would be about right.
Created by Gene Roddenberry. With William Shatner, Leonard Nimoy, DeForest Kelley, Nichelle Nichols. Captain James T. Kirk and the crew of the Starship Enterprise explore the galaxy and defend the United Federation of Planets.