Star Trek Expanded Universe

The USS Excelsior (NCC-2000-B) was a Sovereign-class starship, laid down at Utopia Planitia Fleet Yards in 2371. As of 2373, she was still under construction. (Star Trek: The Adventures of Argus, Star Trek: Liberty)

According to Trekmania, the registry number of this ship was NCC-2000-B, with NCC-2000-A assigned to a Galaxy-class Excelsior.