A fascinating and exceptionally rare École d'Horlogerie de Genève “Pièce d'École”, built around an original Patek Philippe reference 2509 case and movement, and coming directly from the watchmaker who created it as his final examination piece at the Geneva Watchmaking School. Watchmaking school pieces have long fascinated collectors, but examples based on original Patek Philippe components are exceptionally uncommon. Their rarity was recently highlighted when a comparable École d'Horlogerie watch built around a Patek Philippe ref. 2509 case and calibre achieved CHF 91,440 at Christie's Geneva in May 2026, far exceeding its estimate. Christie's emphasized the extraordinary nature of these watches, noting the rarity of the Patek Philippe ref. 2509 itself and the historical significance of such school watches. The present example is particularly appealing as it comes directly from the watchmaker who produced it, providing an exceptional level of provenance rarely encountered. Like the Christie's example, it is powered by an original Patek Philippe movement and housed in an original Patek Philippe ref. 2509 case, a reference distinguished by its sporty water-resistant construction and screw-down caseback. Christie's notes that fewer than a few dozen stainless steel ref. 2509 examples are known today, making the use of such a case for a school watch especially remarkable. The watch remains in completely original condition and appears never to have been polished, preserving the character and craftsmanship of the student watchmaker's work. Every component reflects the traditional standards taught at the Geneva Watchmaking School, an institution that has supplied generations of talented watchmakers to the Swiss watch industry and maintained close ties with Patek Philippe throughout its history. Rarely does a watch combine the worlds of Patek Philippe collecting and traditional Swiss watchmaking education so perfectly. With its original Patek Philippe case and movement, direct provenance from its maker, untouched condition, and historical significance, this is a truly special collector's piece and a rare opportunity to acquire a tangible piece of Geneva watchmaking history.