A-PROOF® Patented Anti-Magnetic System

Just like a human eye

Developed and patented by BALL Watch, the A-PROOF® device is a revolutionary approach to the protection of a mechanical movement against the influence of magnetic fields. It is based on cutting-edge developments in terms of both materials and construction.

The choice of mumetal

BALL Watch carefully selected mumetal for the development of its magnetic trench box located inside the watch’s case. Mumetal is an alloy of nickel, iron, copper and molybdenum with very high magnetic permeability, which enables it to attract and deviate static or low-frequency magnetic field lines.


The diaphragm mechanism

The constant imprisonment of the movement in an anti-magnetic cage has been avoided thanks to an ingenious diaphragm mechanism that extends or retracts at will by simple circular motion of the bezel. In the fully closed position, the diaphragm locks the mumetal anti-magnetic protection cage. In the retracted position, the diaphragm therefore re-opens to reveal the movement at work through a transparent case back. A genuine industrial feat, the diaphragm is machined in mumetal with a thickness of just 0.06mm. A-PROOF® protects a mechanical watch against magnetic fields up to an astonishing record intensity of 80,000A / m.

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