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    NH Movement Rotor - GS 9SA5 - Yellow Gold

    The movement, dressed. GS 9SA5 in yellow gold. Seen through the caseback.

    A decorated rotor turns the one moving part you see through an exhibition caseback — the weight that swings as you wear the watch — into the finished centrepiece of the movement.

    This is a drop-in NH movement rotor — GS 9SA5, finished in yellow gold by PVD (physical vapour deposition), so the colour is part of the metal's surface, not a layer of paint that can chip or peel.

    Swapping it is the simplest mod there is — a single screw, no movement surgery, no watchmaker.

    One screw. Two minutes.
    You're not opening the movement — just trading the bare oscillating weight for a decorated one.

    Seen through the caseback.
    The rotor is the first thing the eye lands on behind an exhibition sapphire — the part that moves. Decorate it and the whole movement reads as considered.

    PVD, not paint.
    The yellow gold is laid down by physical vapour deposition — bonded into the surface, not brushed on. It won't flake, and it can't be stripped back to bare steel.

    A two-minute mod.
    It seats on the rotor post and holds with a single screw. No movement disassembly, no special tools, no risk to the calibre.

    Built for the NH family.
    Machined to Seiko's OEM rotor geometry — 0.15mm thicker to carry the CNC decoration — and tested to fit the full NH, 4R and 7S automatic line.

    To see it, you'll want

    An exhibition caseback. A decorated rotor only shows behind a sapphire (exhibition) caseback — a solid steel caseback hides the movement entirely.

    A matching bridge. For the complete look, pair the rotor with a decorated NH movement bridge in the same finish.

    • Finish & Build

      1. Quality Swiss Production Quality, ISO 9001 Certified
      2. Finish GS 9SA5 · Yellow Gold · PVD coating
      3. Construction 0.15mm thicker than the Seiko OEM rotor, to carry the CNC decoration

      Compatibility

      1. Fit Movements 7S26, 7S36, 4R15, 4R35, 4R36, 6R15, NE15, NH25, NH26, NH34, NH35, NH36, NH37, NH38, NH39, NH70, NH71, NH72
      2. Caseback Exhibition (sapphire) caseback required to display
    • To allow for CNC decoration, the decorated rotor is 0.15mm thicker than the Seiko OEM rotor. Each rotor is tested to fit all our bridges, cases and casebacks.

      Below is Seiko's technical drawing . As long as the case and caseback follow Seiko's OEM specification — a 0.4mm gap between the rotor and caseback — the rotor fits. If those parts deviate from Seiko OEM dimensions, the rotor may be incompatible.

      SEIKO NH Rotor and Caseback clearance drawing
      1. 1x NH Movement Rotor

      All photos of watches with modification parts are for illustration purposes only and are not included with modification parts purchased.

    • Fitting a rotor is the easiest mod there is:

      1. Unscrew the existing rotor screw with a 2–3mm flat screwdriver and lift the old rotor off.
      2. Seat the decorated rotor on the post.
      3. Screw it back down — done.

      New to modding? Start with Seiko Modding: The Complete Build Guide , or browse NH Movements to build around it.

    Questions, Answered

    Everything worth knowing before you build.

    Will a decorated rotor fit my movement?

    Yes — it fits the full Seiko NH automatic family and its relatives: 7S26, 7S36, 4R15/35/36, 6R15, NE15, NH25/26, NH34, NH35, NH36, NH37, NH38, NH39, and the NH70/71/72 skeletons. The rotor screws onto the standard rotor post. What matters is caseback clearance: as long as the case and caseback follow Seiko's OEM specification — a 0.4mm gap between rotor and caseback — it fits. Non-OEM parts with tighter clearance may not.

    Do I need an exhibition caseback to see the rotor?

    Yes. A decorated rotor is only visible through a sapphire (exhibition) caseback. A solid steel caseback covers the movement entirely, so the decoration behind it would never be seen — if your build uses a solid caseback, a decorated rotor won't show.

    Is the finish paint? Will it wear off?

    It isn't paint — it's PVD (physical vapour deposition), bonded into the metal's surface. It won't chip or peel the way a painted coat would, and it can't be stripped back to bare steel; abrasive attempts only ruin the part. Treat the colour as permanent.

    Why is the decorated rotor slightly thicker than a stock Seiko rotor?

    By 0.15mm. That extra material is what lets the decoration be CNC-machined into the face. Every rotor is tested to fit our cases, bridges and casebacks, and the small increase stays within Seiko's OEM clearance.

    Is fitting a decorated rotor difficult?

    No — it's the easiest Seiko mod there is. Unscrew the single rotor screw, lift off the old rotor, seat the decorated one, and screw it back down. There's no movement disassembly and no watchmaker required.