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SKX013 Diver 38 Black Ultra Thin Edition — side profile showing 10.86mm ultra-thin case thickness

Ultra Thin Edition
Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

Seikonaut
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  • SKX013 Diver 38 Black Ultra Thin Edition — side profile showing 10.86mm ultra-thin case thickness

    Ultra Thin Edition
  • Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts

    Seikonaut
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    Seikonaut

    Seikonaut 38mm fully modded in Grade 4 titanium with matching 20mm bracelet — Lucius Atelier Ultra Thin Edition

    The Seikonaut is the modding community's name for a particular kind of build: a Seiko mod that channels the 1970s luxury-sports-watch silhouette — the porthole-shaped case with an integrated-bracelet look that Gérald Genta made famous in 1976. Seiko plus that silhouette. Hence Seikonaut. It's a genre, coined by modders, and we love that it is.

    This page is our take on it. The Lucius Atelier Seikonaut is a 38mm Seiko mod case, designed in-house, built around our Ultra Thin Edition case architecture. Every line of it — the case, the angular flank geometry, the sculpted lug profile — is our own design, engineered from scratch and made exclusively for us by ISO 9001 certified manufacturers. It comes in two materials: 316L stainless steel and Grade 4 titanium.

    What makes ours ours: a genuinely thin profile, a true 38mm bezel sized for wrists the genre's usual 40mm-plus proportions tend to overlook, and the same 28.5mm dial standard shared across the entire Lucius Atelier line. The dials and hands you'd buy for a Bauhaus 33 or an Explorer 36 fit the Seikonaut too. One parts ecosystem, one set of tolerances.

    Steel or titanium — which is right for you?

    Same case, same 38mm silhouette, same 10mm-class thinness. The decision is the material — and it's a real one.

    • 316L Stainless Steel Choose steel for the classic tool-watch experience: reassuring heft on the wrist, a sleek brushed finish, and the familiar weight modders expect from a sports case. The most accessible way into the Seikonaut. Crown style is yours to pick — coin-edge, knurled or onion — and the caseback comes solid or sapphire.
    • Grade 4 Titanium Choose titanium for featherlight comfort: just 29 grams on the case alone, over 40% lighter than the steel version. Grade 4 titanium is harder than 316L steel, naturally corrosion-resistant, and carries its own subtle grey tone. Ships complete — titanium case, titanium coin-edge crown and titanium caseback all included.

    The two cases at a glance

    Case Material Thickness Case weight In the box
    Seikonaut 38mm 316L stainless steel 10.0mm solid / 10.9mm sapphire 49.4g Case body + sapphire crystal (pre-installed) + caseback
    Seikonaut 38mm Titanium Grade 4 titanium 10.0mm solid 29g Case body + sapphire crystal (pre-installed) + crown + caseback

    Both share a 38mm bezel, 42mm full case width with the flared flanks (around 44mm with a 7mm crown), 47mm lug-to-lug and a 20mm lug width. The titanium version ships as a complete case — crown included; the steel version takes any 7mm crown you select. Water resistance is 100m / 10 ATM for the bare case on both — final water resistance of an assembled watch depends on crown, gasket and caseback installation.

    Build it out — the bracelet

    The Seikonaut wears best on a bracelet that flows from the case, and we designed one specifically for it — sculpted around the exact 20mm lug profile so it sits flush, with no awkward gap at the lugs. Two matched options, one for each material:

    • Seikonaut Bracelet 20/16mm The 316L steel bracelet built for the steel Seikonaut — tapered 20mm to 16mm, brushed and polished to match the case.
    • Seikonaut Bracelet 20/16mm — Titanium The same sculpted design in matching Grade 4 titanium, for a full featherlight titanium build.

    But nothing here is locked. The Seikonaut sits on a standard 20mm lug, so the matched bracelet is a recommendation, not a requirement — every other Lucius Atelier bracelet fits, and so does any standard 20mm strap. The case is a foundation; how you finish it is yours to decide.

    Movement & compatibility

    Movements. Both cases fit Type M versions of the NH35, NH36, NH38, NH70, NH71 and NH72 movements. Because the Ultra Thin profile leaves very tight clearance between the hands and the sapphire, Type L movements will not fit — confirm your movement type before ordering. The Seikonaut is recommended for experienced modders.

    Dials & hands. Both cases take 28.5mm dials — the same standard used across the entire Lucius Atelier line — and NH-compatible hands. An SKX013-spec chapter ring is required to seat the dial at the correct height; it's sold separately.

    Crystal. A flat sapphire crystal with anti-reflective coating ships pre-installed and aligned at our Singapore workshop — no crystal-pressing required on your end.

    The sports-luxury silhouette, properly thin and sized for the wrist — designed in-house, made to last.



    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION] - Solid - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION] - Solid - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut 38mm — Ultra Thin Watch Case

    from $120 SGD
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 38mm [ULTRA THIN EDITION / TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut 38mm — Ultra Thin Titanium Watch Case

    $219 SGD
    Seikonaut Bracelet 20/16mm - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Bracelet 20/16mm - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Bracelet 20/16mm

    $99 SGD
    Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Bracelet 20/16mm [TITANIUM] - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Bracelet 20/16mm [TITANIUM]

    $159 SGD
    Seikonaut Watch Case - 36mm - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 36mm - - - - Lucius Atelier - Swiss Quality Seiko Watch Mod Parts
    Seikonaut Watch Case - 36mm

    $239 SGD

    Seikonaut Questions, Answered

    Everything worth knowing before you build — sizing, steel versus titanium, movements, and the parts you'll need.

    Is Seikonaut a Lucius Atelier trademark?

    No — and we wouldn't claim it. "Seikonaut" is a term the watch modding community coined for Seiko mods built in the integrated-bracelet luxury-sports style. We didn't invent the word; we designed our own case for the genre. What's ours is the design: this specific 38mm case, its geometry and its bracelet are all engineered in-house by Lucius Atelier.

    Why does the case look bigger than 38mm?

    The bezel measures 38mm, but the Seikonaut's flared side flanks push the full case width to 42mm — and to around 44mm with a 7mm crown installed. It's a deliberate part of the sports-luxury silhouette: a bold wrist presence on a case that still wears balanced.

    Should I choose steel or titanium?

    Both are the same 38mm case at the same 10mm-class thinness. Steel gives you classic tool-watch heft and a lower entry price; titanium is 29g — over 40% lighter than steel's 49.4g — harder than 316L steel, and naturally corrosion-resistant. Steel if you like the reassuring weight of a sports watch; titanium if all-day featherlight comfort is the priority.

    What's the difference between Type M and Type L?

    Type M and Type L are Seiko's two factory hand-fitting versions of the NH series. Type L sits higher than Type M — about 0.4mm taller from base to second-hand pinion. Because of the tight clearance between hands and sapphire in Ultra Thin Edition cases, only Type M will fit. Confirm your movement type before ordering.

    Does the Seikonaut need a chapter ring?

    Yes. Both Seikonaut cases require an SKX013-spec chapter ring, sold separately. The chapter ring seats the dial at the correct height — without it, the dial sits too low and the hands won't clear. The case fits both normal and ultra thin chapter rings; the choice depends on your dial. If your dial has applied (raised) indices, choose ultra thin for clearance; if flat-printed, either works.

    Will my Lucius Atelier dials and hands fit?

    Yes. The Seikonaut uses the 28.5mm dial standard shared across the entire Lucius Atelier line, so any of our 28.5mm dials and NH-compatible hands will fit. Note that stock SKX007 dials may seat differently — the original SKX007 has a 4 o'clock crown position with offset dial feet, while our case is designed for 3 o'clock dial feet.

    Do I need to press the crystal myself?

    No. The flat sapphire crystal ships pre-installed and aligned at our Singapore workshop. The chapter ring sits on top of the dial, inside the case — not under the crystal — so the crystal stays put throughout your build.