anyhow,,,,
while it's true S&W never used a copper wash the older nickel plating was and is a bugger to fix.... other than replating..best bet depending on how deep the pitting is to to use a "light abrasive" (600 is probally the heaviest) and working down to the finest grade you can find. (auto parts stores are great for this)
then "blending" in the area with either mothers mag or flitz polish..you can get a mirror shine and it could be possable to even get something close to a match in finish...however,,, now your down to bare steel..you would probally want to treat it with a good gun wax, and keep an eye on that area for any rust or discoloration and repolishing & waxing when nessary
and as for nickel plating..... heres an explanation of electroless nickel plating...
Electroless nickel plating is an auto-catalytic reaction used to deposit a coating of nickel on a substrate. Unlike electroplating, it is not necessary to pass an electric current through the solution to form a deposit. This plating technique is to prevent corrosion and wear. EN techniques can also be used to manufacture composite coatings by suspending powder in the bath.
Electroless nickel plating has several advantages versus electroplating. Free from flux-density and power supply issues, it provides an even deposit regardless of workpiece geometry, and with the proper pre-plate catalyst, can deposit on non-conductive surfaces.
Pretreatment of parts for EN plating
Before performing electroless nickel plating, the material to be plated must be cleaned by a series of cleaning chemicals such as bases and acids, this process is called the pre-treatment process. Failure to remove unwanted "soils" from the part's surface would result in poor plating. Each pre-treatment chemical must be followed by water rinsing (normally two to three times) to remove the chemical that adheres to the surface. Degreasing removes oils from surface; acid cleaning removes scaling. Activation is done with a weak acid etch, or nickel strike, or, in the case of non-metallic substrate, a proprietary solution. After the plating process, plated materials must be finished with an anti-oxidation or anti-tarnish chemical (trisodium phosphate, chromate etc) and pure water rinsing to prevent unwanted stains. The rinsing materials must then be completely dried off or sometimes baked off to obtain the full hardness of the plating film.
