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Seikonaut Watch Case - 36mm

The First Seikonaut at 36mm — A Complete Integrated-Bracelet Case.

For those who like it small: the first-ever Seikonaut at 36mm. With its side notches it reaches 40.5mm, and 43mm including the crown — so a 36mm case wears with closer to a 40mm presence. Small, but a statement.

The sapphire crystal is coated with clear anti-reflective on both surfaces — double-sided AR — for an almost crystal-less view of your dial and hands. It comes as a complete case with an integrated bracelet designed specifically for it.

Everything but the dial, hands and movement is included. Tested to 200m.

A complete case — sapphire, crown, caseback and bracelet, all in.
Just add a dial, hands and movement. The integrated bracelet and double-sided AR sapphire are built in; there’s nothing to press or fit.

36mm that wears like 40.
Diameter 36mm — 40.5mm across the side notches, 43mm including the crown. A compact case with real wrist presence. Fits wrists from 13–20cm.

Double-sided AR sapphire.
Both surfaces of the flat sapphire carry clear anti-reflective coating (28 × 1.5mm), for a clarity that makes the crystal nearly disappear over your dial.

Integrated bracelet, built in.
A bracelet designed specifically for this case, with a 14.1mm integrated lug. Additional links can be supplied for larger wrists.

Complete and sealed.
Ships with sapphire, a screw-down crown, a clear sapphire screw-down caseback and the bracelet — all included. Rated to 200m.

Heads up — sold separately

Dial, hands & movement. The only parts chosen separately. Match the dial and hands to your NH movement (date / day-date / no-date).

Everything else — sapphire crystal, crown, caseback and integrated bracelet — is included. No chapter ring needed; dials seat on the grey dial holding spacer.

  • Dimensions

    1. Case Diameter 36mm (40.5mm across side notches, 43mm including crown)
    2. Case Thickness 12.2mm
    3. Lug to Lug 43mm
    4. Lug Width 14.1mm (integrated bracelet)
    5. Fit Wrist 13cm–20cm (additional links available)

    Materials & Finish

    1. Quality Swiss Production Quality, ISO 9001 Certified
    2. Case Material 316L Stainless Steel
    3. Crystal Flat sapphire, double-sided clear anti-reflective coating
    4. Crystal Size 28mm × 1.5mm
    5. Caseback Screw-down, clear sapphire
    6. Crown Screw-down, included

    Compatibility

    1. Movements Seiko NH35, NH36, NH37, NH38, NH39, NH70, NH71, NH72 (not NH34 / GMT)
    2. Dials 28.5mm — fits all our dials (seats on the grey dial holding spacer)
    3. Bracelet Integrated, included

    Water Resistance

    1. Water Resistant 200m / 20 ATM
  • The simplest build we make: the case is complete with crystal, crown, caseback and integrated bracelet. Add only a dial, hands and movement.

    What's already in this purchase:

    The complete watch case — flat double-sided AR sapphire, screw-down crown, clear sapphire screw-down caseback, and the integrated bracelet.

    The 3 parts you'll need for a complete watch:

    1. Dial (28.5mm) Seats on the grey dial holding spacer — no chapter ring required. Match it to your NH movement.
    2. Hands Paired with your dial.
    3. Movement Seiko NH35/36/38 (and NH70/71/72). Not NH34 / GMT compatible.

    Optional finishing touches:

    1. Decorated bridge + rotor (visible through the clear sapphire caseback) — replace the stock NH bridge and rotor with our Côtes de Genève set. Our bridges fit only our rotors (not OEM Seiko rotors), so they’re chosen as a pair. Recommended for experienced modders only.

    Want it built for you?

    Tick the Assemble Watch option above and we’ll handle the full build in our Singapore workshop — case fitting, movement seating, crown alignment, caseback press and a function check.

    Heads up: assembled watches require 2–5 business days of workshop time before shipping.

    Once your parts arrive, see the How To Mod tab for assembly tutorials.

    1. 1x Watch Case (includes sapphire crystal, screw-down crown, clear sapphire caseback and integrated bracelet)

    Only the dial, hands and movement are selected separately to complete your build.

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

    1. A Complete Guide On How To Mod Your SEIKO Watch Dial And Hands (Photos & Video)
    2. Fitting dials with four dial legs
    3. Seiko Modding: The Complete Build Guide (2026)

Questions, Answered

Everything worth knowing before you build.

Which movements fit the Seikonaut Watch Case 36mm?

Seiko NH only — NH35, NH36, NH37, NH38, NH39, NH70, NH71 and NH72 — seating on the grey dial holding spacer (no chapter ring needed). It is not built for the NH34, and it doesn't take Swiss ETA or Sellita movements. The case ships complete — sapphire crystal, screw-down crown, clear sapphire caseback and integrated bracelet — so only the dial, hands and movement are chosen separately.

Is the bracelet on the Seikonaut Watch Case 36mm included, and can I swap it?

Yes — the integrated bracelet is included and designed specifically for this case. Because it's integrated (14.1mm at the case), it isn't a standard 20mm-lug bracelet and doesn't swap for off-the-shelf straps. For larger wrists, additional links can be supplied (it fits 13–20cm as shipped).