Smith & Wesson Model 100 Melonite handcuffs. Used on S&W's guns, the new melonite finish provides a new level of durability and scratch and rust resistance in handcuffs. Historically, handcuff makers have used black oxide which is an oxidation process that is only a few millionths of an inch thick. That process does not offer much corrosion resistance, and doesn't alter the underlying steel. Melonite is a case hardening process that leaves a relatively thick, corrosion resistant, hard surface.