The USS Yamato (NCC-1305-E) was an unmanned illusory reproduction of the USS Yamato.
In early 2365, it was created by the entity known as Nagilum inside a "hole in space". The reproduction had corridor walls made out of a material similar to tritanium and was created to study the reactions of the Enterprise-D crew. The real USS Yamato was at the time located in another quadrant of space away from the "hole in space" that appeared en route to the Morgana Quadrant from the Rachelis system. Lieutenant Worf and Commander Riker investigated the reproduction before it was erased by Nagilum. (TNG: "Where Silence Has Lease")
Background information[]
The Yamato's registry was identified by dialogue in "Where Silence Has Lease" by Riker who visually identified it from the hull of Nagilum's reproduction and stated it to be "NCC-1305-E". The Yamato listed on a Starship Deploy Status in "The Measure Of A Man", the starship had the registry "NCC-24383". However, with its later appearance in "Contagion", several computer screens, schematics and captain's logs identified the registry as "NCC-71807".
According to Star Trek Encyclopedia, 4th ed., vol. 2, p. 505, the initial NCC-1305-E registry number was a production mistake. It was given to the Yamato by the episode writer Jack B. Sowards, who was unaware of the registry numbering scheme developed for Star Trek: The Next Generation. Michael Okuda had intended to correct the number, as he had already finished the decals for the saucer section of the model for "Contagion", but as the scene was removed from an intermediate draft, he dropped the issue, only to find out the scene had been re-added later on to the final draft, which Okuda realized after the episode had aired.
The dedication plaque of Nagilum's recreation of the Yamato was seen in the episode, but it was a reuse of the Enterprise-D plaque. In the remastered version of the episode, the plaque was blurred in post production to hide the fact.