USS Essex was a Constitution-class, Bonhomme Richard-subclass starship active in Starfleet service in the second half of the 23rd century. (Star Trek Encyclopedia) One source has the registry as NCC-1697; however, the Star Fleet Technical Manual had the Essex's registry as NCC-1727. The Essex made first contact with the Sheliak and would later play a key role in establishing the Treaty of Armens between the Sheliak and the Federation. (Ship Recognition Manual, Volume 4: Starships of the Original Series Era)