Chronometer Manufacture Caliber RRM7309-S. Inspired by the exacting standards set by our trailblazer Webb C. Ball in 1891, the new caliber delivers next-level precision: accuracy range of -2/+5 seconds per day, a silicon balance spring and 2,500 Gauss anti-magnetism. In the creation of the RRM7309-S, our watchmakers combined new material with traditional watchmaking and created something truly marvelous. As a material choice, silicon offers high anti-magnetism and corrosion resistance, it also offers enhanced stability to temperature fluctuations. The result of years long development is the all-new Manufacture Caliber RRM7309-S, with extreme anti-magnetic protection to 2,500 Gauss, enhanced shock resistance and most importantly, a 30% increase in precision as compare to the COSC standard.