Howdy TC,
From the NCOWS Rules:
No matt-finished or brushed-finish stainless steel firearms are allowed except as specifically exempted in these Rules and Regulations, e.g. only those stainless steel firearms whose finish resembles an original nickel-plated finish.
For example, the USFA revolver with the matt-finish [Rodeo IIRC] must have the finish smoothed to be NCOWS legal. I would read this rule as prohibiting "satin nickel" finish. PM Trap who is here in CAS City. He is the NCOWS Judge and has the final say.