The winterized T-51b is probally the closest thing to original power armor. With it never degrading, it always stays 45 dt. Hellfire armor is always degrading...
That's because of a bug. You get the simulation version rather than the wasteland version of winterized.
Are you the Ruler of Lore?
No, it's the game. Winterized is 45 DR. Regular is 50 DR. Gameplay mechanics is lore.