The Fed Old Heavy Cruiser is built on an enlarged version of the hull of the Texas-class CL (aka the Old Light Cruiser). Intended as a competing design to the Constitution-class CA, the ship didn't make the cut. Only two were ever constructed - NCC-1361 Alfred the Great and NCC-1362 Theodoric the Great. A third ship, NCC-1363 Alexander the Great was planned but never built. Historically, the Alfred the Great was destroyed during the Romulan incursion depicted in the Star Trek: TOS episode "Balance of Terror." While the CA Enterprise was fighting the Romulans on one end of the Neutral Zone, the OCA AtG was similarly (but less successfully) engaged at the other end of the line.

Note that the version presented here is taken from the Fed Com ship card, which depicts a fully refitted "General War version" of the OCA which never existed in the more historically rigorous SFB timeline, hence the addition of ph-3s and a drone/ADD rack, the standard defensive fire package which formed the Federation Star Fleet's Y175 refit.

Thanks to Mike West and Will McCammon on the ADB Fed Com Forum for info on the names and history of the OCAs.