AT: "nt" The Armstrong-type was a medium sized starship class in service to Starfleet in an alternate reality set in the mid-23rd century. A typical ship of this type had two active outboard nacelles and a ‘dummy’ inboard nacelle. These nacelles were connected by swept pylons to the underside of the primary hull. Similar to the Miranda-class starship in the regular reality, a Armstrong-type starship was equipped with a rollbar supporting a multi-tube torpedo launcher. Extending from the trailing edge of the primary hull, and connected to the rollbar by smaller pylons, there was a structure housing the impulse drive. This type participated in the pivotal Battle of Vulcan in 2258, and was named after the USS Armstrong. (Star Trek)
An alternate name for a ship of this type was the USS Excelsior (NCC-1729). This ship, colored brown, was seen in concept art from Star Trek - The Art of the Film.