USS Pegasus was an Oberth-class ship lost in 2358. In 2370, the USS Enterprise D rediscovered her with half of the ship materialized within solid rock (TNG: The Pegasus).
Originally not intended as an Oberth-class ship, but rather a kitbash made from the Enterprise C model, creating a more compact design.
Since we don’t have a class name, I named it the Waitomo-class. It is based on an original concept drawing by Rick Sternbach. Sadly the design was never realized. Due to the expensive external shots of the asteroid belt and the asteroid interior in that episode, there simply wasn’t enough budget left to create the ship, so they just used the studio model of the USS Grissom (seen in Star Trek III: The Search for Spock).
Check out the Artstation post for more info: https://www.artstation.com/artwork/XnA4vL