The finish on the MM is a nickle -Teflon coating that has some very desirable qualities. It is conductive, very scratch resistant and very protective of the aluminum body in the presence of salt water or sweat. It does form a thin layer of nickle tarnish over time and exposure to corrosive elements. The tarnish is not harmful but is a cosmetic fault. We tried other none tarnishing finishes such as smooth nickle, chrome over nickle and gold over nickle and found that they looked great but a small pinhole in the finish allowed major destruction of the aluminum under the finish. A small pinhole rapidly grew into a large blister in the presence of salt water. The Teflon nickle finish kept the damage isolated to the original pinhole.
We tried 6 tarnish removers and found one that works very well, is readily available, and has been around for more than a hundred years. Other polishes worked but not as easily or well. The tarnish remover is Wright's Silver Polish and can be found in almost any grocery. It's also available on the web.
Simply follow the directions on the container.