COSC certification

Longines has decided to equip two of its exclusive mechanical movements — the L888.4 and the L592.4 — with a monocrystalline silicon balance-spring offering unique properties. The balance-spring is the watch's regulating organ. Coupled to the balance, it oscillates around its position of equilibrium, thereby exercising its fundamental role: to maintain a regular rhythm. Magnetism, temperature variations or wear (several hundred million “beats” per year) can all disrupt normal operation. To increase accuracy and durability, Longines has opted to use monocrystalline silicon balance-springs in its two flagship mechanical movements. This material is strong, light, stainless, and resistant to normal temperature

variations, magnetic fields, and atmospheric pressure. In light of the high accuracy offered by this silicon balance-spring, Longines decided to have the new calibres certified as “chronometers” by COSC. All the pieces are therefore tested individually by this neutral, independent organisation, enabling their dials to be stamped with “CHRONOMETER”. Watches equipped with these calibres are accompanied by a Longines certificate. The COSC certificate can be purchased separately.