Echoing the technical characteristics and record-breaking 3.5 mm measurement of the 600P tourbillon movement, the 640P movement is, just like its predecessor, the world's thinnest tourbillon movement. It features a flying tourbillon, positioned at 12 o'clock, whose carriage is accentuated by the presence of the stylised "P" of Piaget. The asymmetry of the design required meticulous adjustments in order to respect the balance of the whole movement. This carriage contains its regulating organ: the balance spring. The 640P movement is characterised by the addition of an astronomical moon-phase indicator at 6 o'clock. Governed by a gear train of extreme finesse, it will lose only one day every 122 years. In keeping with the tradition of Piaget's work with hard stones, it is enhanced by a disk of lapis lazuli, with two 18k gold pellets, and follows the moon phases with an exacting precision. Finally, the decorative elements such as the circular Côtes de Genève, circular-grained mainplate, bevelled and hand-drawn bridges and blued screws keep with the distinctive aesthetic codes of the Swiss watch brand.