Magnetic Resistance The Milgauss was developed for scientists and engineers working in magnetic environments. Its innovative design resists interference while maintaining Rolexs signature precision and style. Scientific Precision This 40mm Milgauss from 2009 features a black dial and smooth bezel in Oystersteel. Powered by the calibre 3131, it offers a 48-hour power reserve and is fitted with an Oyster bracelet and Easylink Oysterclasp. A distinctive lightning-bolt seconds hand adds a bold finishing touch.