The winding crown is one of the elements most exposed to strains, manipulation and, consequently, wear. The length of the power reserve and the consequent regularity with which a watch must be wound are therefore crucial elements for its proper functioning, particularly for a professional instrument designed for ultimate reliability and accuracy. The challenge of a long power reserve, which enables the watch to run uninterruptedly for more than a week without requiring any manual intervention, was tackled by Panerai at the beginning of the 1940s when it used a hand-wound Angelus® movement with eight days of power reserve, a very solid, reliable calibre. These characteristics were vital for the Panerai watches used by the underwater commandos of the Royal Italian Navy, which had to be reliable even in the most extreme conditions of use. The long power reserve, significantly reduced the manipulations on the winding crown, which improved durability and helped to maintain waterresistance. Thus it became one of the distinctive elements of the Panerai watch and part of the DNA of the brand. It is indeed no coincidence that the first movement (P.2002) from the Panerai Manufacture in Neuchâtel in 2005 was a calibre with a power reserve of eight days and that the P.5000 movement has the same characteristic in honour of the tradition and history of Officine Panerai.