I wouldn't call it a Sean Bradley helmet... but I pulled those casts...
Long before I made helmets, I made a few 'as -is' pulls from a badly designed mold that I threw together before I completed my helmet. I sold them for real cheap in the Classified section here... in fact some industrious member could probably still find the thread up there.
Anyway this particular helmet was bought by someone who didn't take the time to finish it properly. He just threw a coat of paint on it and put it up on eBay... much to my disaproval.
It'd sure be swell if the 'Halo Museum' knew the slightest thing about what they were talking about before they posted up images they stole from somebodys auction on ebay...