>>89081341As I understand it, they were unable to replicate the Advanced Power Armor after the events of Fallout 2, and were seeking alternatives. The MkII was inferior in every aspect besides being cheaper and easier to mass produce, and wasn't even as good as the T-56b. The Duraframe Hellfire Armor was another attempt to bring them closer to re-creating something similar to the original Advanced Power Armor.
I have noticed however that the Advanced Power Armor MkII strongly resembles the Brotherhood of Steel Advanced Power Armor from Tactics, and Bethesda may have simply mistaken it for Enclave armor.
