Ball Watch takes on one of mechanical watchmaking’s arch enemies – magnetic fields – and sparks a technology revolution in the process. Whereas “anti-magnetic” movements are expected to resist a magnetic field of at least 4,800 A/m, the new A-PROOF® system guarantees protection up to 80,000 A/m. Its secret is a shield that closes over the movement. It is made from mumetal, an innovative alloy in watchmaking whose high magnetic permeability attracts or redirects lines from static or low-frequency magnetic fields. And this isn’t the only innovation. Unlike conventional anti-magnetic systems which enclose the movement in a cage, Ball Watch protects its mechanism with an ultra-fine diaphragm in mumetal, just 6/100th mm thick, that is operated by the rotating bezel. Leave it open to admire the movement of the Engineer II Magneto S through the sapphire back, or close it to “lock” the mumetal shield and protect against magnetic fields. Model Reference: NM3022C-N1CJ-BK