It is not uncommon for Patek Philippe to case and sell their most complicated and valuable movements sometimes even years after their initial production. This is the case here as it wasn’t until 1935 that this perpetual calendar minute repeating movement was first sold, having been made 10 years earlier in 1925. It is even more fascinating that already 3 years later (in 1938) the watch returned to Patek Philippe and was upgraded with a number of new features: a new reference 600 case in yellow gold, together with a state-of-the-art black dial, very much en vogue in the late 1930s. Most likely, the current black dial was installed on this occasion as well. Even the movement was modernised, receiving a Glucydur balance, invented only a few years earlier. The advantage of this balance lies in the alloy composed of beryllium and copper providing greatest stability for a wider spectrum of temperatures. The screw-less design enjoys furthermore greater aerodynamic efficiency.

Few complicated Patek Philippe pocket watches are known from the pre-war era and the present example, preserved in excellent and all original condition, is an extraordinary collector’s watch: it not only embodies Patek Philippe's ethos of being at the forefront of watchmaking innovation, but also represents one of the most attractive vintage pocket proposition of the company in virtue of its black dial.