Most weapons of the WWII to Korea and later for service use were a "Parkerized" finish. The 1911 I was issued in the USMC circa late '60's was. It is a phosphate coating without sheen. It is usually a zinc or manganese phosphate coating that cannot be applied to an alloy framed weapon. The finish holds up quite well, e.g. M-1 Garands other than the stainless piston under the end of the barrel at the business end of the weapon. It does not work on a high nickel steel, for that you have passavation. I have several G.I. magazines made for M-9 use that I use in my Beretta 92FS that are parkerized as well. Don't know who makes them, butr they function flawlessly. If you want to change the finish to a hard chrome or electroless nickel finish post parkerization, the finish will have to be stripped which may involve some loss of detail such as impressed stampings in the slide/frame of a steel weapon as you must remove the parkerization entirely. There are some new finishes out there that resemble parkerization and are like a powder coat that work very well that you might want to consider. In the '80's I did some work in a friend's gunshop making copies of the S&W ASP design, right down to the sight system, purchased separately, and we applied a teflon finish to the weapons. Even used lexan for grip panels for the see through magazine capacity verification after cutting the side panels on the model 39 magazines. The mag butt extension was t-6 aluminum that we teflon coated as well. Great little carry weapons!! Did some on 59's as well that gave you increased capacity at the cost of more grip thickness. Sorry, off the subject. Hope this helped.