Swatch caliber Sistem51-M HM

The SISTEM51 Manual-Wound is a hand-wound mechanical movement developed by Swatch for the Audemars Piguet × Swatch Royal Pop collection. It is based on Swatch’s SISTEM51 architecture, here adapted to a manually wound format and used in the Lépine-style Royal Pop models with central hours and minutes only. The movement is part of the SISTEM51 family, known for its fully automated Swiss assembly. In this hand-wound Royal Pop version, it is specified with 15 active patents, a Nivachron balance spring, and factory-set precision adjusted by laser. The movement offers a power reserve of more than 90 hours. A distinctive feature of this execution is its barrel drum, which also functions as a power-reserve indication. When the barrel chambers appear grey, the coils of the mainspring are visible and the movement requires winding. When the chambers appear gold, the mainspring is fully compressed and the movement is fully wound. In the Royal Pop watches, the movement is partially visible through a transparent case back.