The Bulwark battlecruiser is one of several ships from Rebellion ever referenced outside of that game. The Bulwark Mk. I was mentioned in The New Essential Chronology and I believe Dan Wallace (the author) said that he intentionally named it with a Mk. I tag, because the ship in Rebellion is much, much bigger (being able to challenge an Executor Star Dreadnought or at least be a Rebel commandship like that). So that would have to be either a Mk. II or Mk. III model. Even the Mk. I, being only 1,000 meters long, was quite impressive at the time (since it's shaped like one of those exotic fish-species that are as tall as they are long, it adds greatly to the volume of the ship, giving it more space to put guns, than on those other thin, skeletal vessels in the CIS Navy).