In an effort to keep things simple, NCOWS tries not to over-legislate. When looking at a revolver and it's "not on the list", ask yourself: did this weapon in my hand exist 1865 to 1899? If you don't know, hit the books or post a question here.
Did a brushed or matte or satin metallic finish exist back then? Not that I can locate. Gold plate, silver plate, French grey, nickel, bluing (a variety, all shiny) and 'in the white' are all documented.
Our general firearm covenant states:
No modern (post 1899) firearms will be allowed unless they are authentic reproductions of traditional firearms or very markedly resemble traditional firearms. Traditional firearms are defined as those manufactured prior to or during the era 1865-1899 and in documented use on the North American Frontier within that time period. Center-fire calibers may substitute for original rim-fire calibers in reproduction firearms. Reproduction firearms chambered in calibers not utilized in original models shall be allowed as long as such calibers are original to the period or are otherwise approved by the National Congress of Old West Shootists.
One of the important facets of NCOWS is our "look". One of our goals at every match is to look around and not see anything that looks like the 20th (or 21st) century.
Do we scrutinize each other: yes. (in a friendly manner & mostly amongst the established or veteran members.). The scrutiny is held to a higher standard at "big matches".
I for one enjoy the scrutiny. It usually evolves into a lively discussion where we all learn something new. I like that.
And, if you think your item (matte finish in this case) should be authorized, prepare some historic documentation of your claim and approach our Authenticity Committee.