Watch SafeHorology glossaryDefined term / rotor
Rotor
The weighted mass in an automatic movement that swings with wrist motion to wind the mainspring, mounted centrally on most calibers or as a smaller off-center micro-rotor.
Authentication note
Why this detail matters.
Rotor engraving, finishing, and shape are caliber-specific and visible through an exhibition caseback or during inspection. Counterfeits often reuse one generic rotor across supposed calibers, or engrave text with the wrong font and depth. A noisy or wobbling rotor can also signal a low-grade replacement movement inside a genuine-looking case.