Accompanied by Patek Philippe Extract from the Archives confirming production of the present watch in 1925 and its subsequent sale on 13 December 1935. It furthermore states that in 1938, the original case was replaced by the actual one bearing number 618'751.
A particularity of the present watch is its balance, the so-called Glucydur balance, introduced in the market around 1935. The smooth two or three arm balance 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 screw less design also has a greater aerodynamic efficiency.