The Belfast Class Medium Cruiser was an unorthodox design put into service by Starfleet around the same time as the Constitution Class Heavy Cruiser. As expected, the Belfast didn't perform nearly as well as other cruiser types of the era. Several vessels of the class would however receive complete refits after the so called "Whale Probe" incident.

*Sidenote: I based this on an old image that had once been of the Wolf's Shipyard website before CanisD removed all images that he didn't make. So, as such I have no clue as to whom created the Belfast in the first place.