Glucydur

Glucydur is an alloy of copper, beryllium and iron. This alloy has special mechanical properties. Glucydur is antimagnetic, resistant to corrosion, has a hardness of 400 Brinell and a low thermal expansion coefficient.

The alloy is most commonly used in watch movements of bracelet or pocket watches for monometallic unrest as part of the transition controller because of its elasticity and stability.

The word is from the French words glucinium ( an old name for beryllium) and dur (French for hard) together.