Automatic watch accuracy is easily affected by magnetic fields. Even a brief contact with a man-made magnet, which is very common in our daily lives, could lead to magnetization of an unprotected automatic movement.
What does the term "antimagnetic" actually mean? The existing standard is defined thusly: if a mechanical watch does not stop when exposed to a magnetic field of 4,800 A/m and subsequently does not deviate by more than 30 seconds per day, it can be called "antimagnetic." Our antimagnetic collections employ a special case design constructed with corrosion-resistant ferrite stainless steel materials and are specially equipped with an inner soft iron jacket consisting of a back plate, a ring surrounding the movement and the dial. This special alloy, reinforced by the shape of the inner case, prevents magnetic fields from penetrating as far as the movement and having an adverse effect on the watch's accuracy.
The ultimate explorer watch, the BALL Engineer Hydrocarbon, far surpasses the common standard with a magnetic tolerance up to 12,000A/m.