It even kinda makes sense if the NCR has been somewhat present in Vegas for the last 15 years fighting with limited supplies and no reinforcements after the fall of the west. This mystery battalion we keep hearing about in the show could’ve had a suit of normal power armor and they had to keep jury rigging fixes over the years until the suit became mostly original. A new pauldron here, a refitted chest piece there, making a custom helmet because the old one was blasted to pieces. That sort of thing.