The splitting of the light mentioned above then takes place both on the surface of the glass and also on the surface of the thin anti-reflective layer.The light reflected from this layer overlaps with that from the glass itself.
The adjustment screws inserted on the sides were used to individually compensate the large temperature error of earlier steel balance springs and to carry out the basic adjustment of the movement.
Multiple layers with different types of coating and thicknesses are required to create an anti-reflective effect at different wavelengths (colours) of visible light.
Sinn's sapphire crystals are always coated on both sides to ensure optimum readability.
DIN guideline 8309 stipulates that mechanical watches are antimagnetic if their rate change does not exceed /- 30 seconds per day after exposure to a magnetic field of 4,800 A/m (corresponds to 6 m T) (movement diameter larger than 20 mm).
The watch should also not stop when exposed to a magnetic field of this strength.