Tissot Watch PRX 35mm Light Green T1372101109100. Because the magnetic fields generated by our electronic objects (mobile phone, computer, radio, magnetic closure, etc.) are ever more present in our daily lives, Tissot has developed a new, titanium-based alloy at the cutting edge to preserve the precision of its watches. A Nivachron balance spring is regarded as far more resistant to and unaffected by magnetic fields than standard springs.