Zenith. A rare and unusual silver openface two-day deck chronometer with power reserve and Glucydur balance

With brass-bound wooden box.

Zenith's 20 lignes calibre 5011K, featuring a lever escapement, anti-shock device, Breguet regulator, Glucydur balance and non-magnetic hairspring, was introduced in 1960. In 1967 the celebrated movement received the most awards of all times at the Neuchâtel Observatory.

The so-called Glucydur balance was introduced in the market around 1935, at the same time as the Nivarox balance spring. The smooth two or three arm balance is composed of an alloy of mostly beryllium and copper provides excellent hardness and high stability over a wide range of temperatures. The combination with a Nivarox spring providing temperature correction does make balance screws unnecessary for this purpose. The screwless design also has a greater aerodynamic efficiency.