I must admit, I follow all the stories of people trying to remember what was 100% - like the dome being shiny or slightly matt. But for me, I see what I see on the film, and that's my reference point. I know there were many versions done of the various parts of the costume, but that entrance into the Tantive IV - that's Vader to me.
So all my reference comes from that opening sequence.
Point in case; anyone can tell me the dome has a matt or statin finish - that's fine - but my eyes (clear as day) see a gloss finished helmet. Now people can tell me it's lighting, but I've worked on film sets for the past 25 years and can tell you firsthand, lighting can't make it look as gloss as it does in that Tantive IV sequence.
So again for me, it comes down to this. Do I give a crap about the tiniest of details when it's up on my shelf? Or am I jazzed just to have such a great looking figure, that - standing distance away, looks outstanding.... be it Vader or any other collectible.
Each to their own.