Swatch caliber Sistem51-M HMS

The SISTEM51 Manual-Wound Small Seconds is a hand-wound mechanical movement used in the Savonnette-style models of the Audemars Piguet × Swatch Royal Pop collection. It shares the same basic SISTEM51 architecture as the central-display version, but adds a small seconds indication positioned at 6 o’clock on the dial. This movement is specified with 15 active patents, a Nivachron balance spring, laser-based factory precision adjustment, and a power reserve of more than 90 hours. As part of the SISTEM51 family, its construction is linked to Swatch’s automated Swiss movement assembly system, here adapted to a hand-wound configuration. The Royal Pop execution also uses the barrel drum as a visible power-reserve indication. Grey barrel chambers reveal the coils of the mainspring and indicate that the movement needs winding, while gold chambers indicate a fully compressed mainspring and a fully wound state. The movement is partially visible through the transparent case back, which forms part of the Royal Pop’s pocket-watch construction.