Why was Vader so feared by the soldiers of the Rebellion? The last few minutes of Rogue One answer that question very clearly.
Again, the props department couldn't resist messing with a design just a little bit, even though it technically needed to lead right into A New Hope as far as continuity went. As such, the gunmetal grey is spray painted rather than brushed, though at least they managed to restrain themselves from giving it a thick coat of gloss lacquer. The dome is highly polished rather than gloss coated, and we replicate this finish with extensive hand sanding and polishing.
We happen to know quite a bit more about this helmet than the others, and the reason is that it was actually our helmet that was used as the master for the prop department on Rogue One! Vader as a character was something of a last minute addition to the movie, and so they were left scrambling to produce a costume. Crew members were asked if they could help out, and a couple of members of the production volunteered the use of their Vader helmets. The face from our helmet was chosen to be used in conjunction with a separate dome. It was handed off to a model maker for a little bit of fettling (apparently some of the more organic lines that Vader's helmet is well known for among collectors were judged unsuitable for HD cameras), but the basic shape was left unchanged. It really was incredible to be even such a small part of the Star Wars universe.
The pictures above are not final, new photos are coming soon