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Seikonaut Watch Case - 36mm

ONLY 4 main components are needed to complete a watch.
Watch Case
Bridge & Rotor (optional)
Movement Holder (optional)
Tweezer (optional)


  • For a complete watch, select your (1) Dial, (2) Hands and (3) Movement.
  • To decorate movement, select your (4) Bridge and Rotor (optional).
  • To have watch assembled, select (5) Assemble Watch. Please note that assembling the entire timepiece requires 2 to 5 business days prior to shipping.

Engineered by us and made exclusively for us with quality assurance by ISO 9001 Certified manufacturers.


Rejoice for those who like it small, the first ever Seikonaut @ 36mm! Including the side notches and crown, it goes up to 40.5mm and 43mm, respectively. Thus, giving this 36mm case a 40mm presence on wrist. Small, yet a huge statement.

Additionally, you will get an extremely crystal clear view of the dial and hands you would think there was no crystal in place. This was achieved by having both the outer surface and inner surface of the sapphire crystal coated with clear anti-reflective coating, also known as double sided AR coating. A simple procedure that brings new joy to visually appreciating your own mods.

Together with an integrated bracelet designed specially for this case.

**Designed to fit all of our dials (28.5mm) and original NH movements (grey dial holding spacer). Not suitable for GMT NH34 movement.
    1. Quality Swiss Production Quality, ISO 9001 Certified
    2. Case Material 316L Stainless Steel
    3. Case Diameter 36mm, 40.5mm with side notches, 43mm with crown
    4. Case Thickness 12.2mm
    5. Lug to Lug 43mm
    6. Lug Width 14.1mm
    7. Caseback Screw down, Clear Sapphire
    8. Crown Screw down
    9. Crystal Flat Sapphire with Double Sided Clear Anti-Reflective Coating
    10. Crystal Size 28mm x 1.5mm
    11. Water Resistant 200m / 20atm
    12. Fit Wrist Circumference 13cm to 20cm (Additional links can be provided for bigger wrist size)
    13. Fit Movements NH35, NH36, NH37, NH38, NH39, NH70, NH71, NH72
    1. 1x Watch Case (Inclusive of sapphire, crown, caseback, bracelet)

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

  • Recommended Mods With:

    1. Swiss Super-LumiNova® BGW9 Hands
    1. A Complete Guide On How To Mod Your SEIKO Watch Dial And Hands (Includes Photos & Video)
    2. Learn about fitting dials with four dial legs

Customer Reviews

Based on 18 reviews
jason p. (San Jose, US)
LOVE the LA 36mm Seikonaut

This is my perfect size watch size and in line with the current trend back to 36mm cases. The new dark blue dial offering made it a must buy with that perfect gradient outer edges and machined horizontal layers. Wore the watch today and non-people complimented it and a random stranger came up to ask if it was a 5711.

The bracelet tapers as it should and is of very good quality. Case is also similar and I'm loving the bezel to dial ratio much more on the 36mm

Adriel was extremely responsive and I really appreciate the hand written card I received with this watch, thank you for providing amazing mods and custom parts!

Frédéric C. (Bruges, BE)
Using this mod part for: Seikonaut case 36 mm
Amazing customer support

Great product and amazing customer support!

T. B. (Amsterdam, NL)

Amazing build quality, very satisfied with the product. Would definitely recommend.

JRivera (Guilford, US)
Using this mod part for: Seikonaut 36mm
My Tiffany Seikonaut 36mm

Stunning case and bracelet, great quality. Amazing super-fast shipping and delivery is outstanding. It looks so classy. It looks better in person. I cannot thank Lucius enough, thank you for precutting the stem to fit my Seiko NH movement. This is my favorite watch mod from all my previous ones. Perfect size, the 36mm wears like a 40mm. Thank you. Jorge from CT, USA.

Gideon M. (Dublin, IE)
High Quality product

Product arrived with no problems during delivery and looks/feels very premium. Will definitely be ordering more in the future

Scott M. (DeWitt, US)
Great case and bracelet

Great case and great service. Will be making future purchases.

J.L. (Livonia, US)
Great watch and fast shipping

Very professional, 6 day shipping to U.S..... thank you!

Harley (Charleston, US)
Outstanding Quality

Amazing quality! the bracelet looks incredible and a super fun case to mod with!

Andrew Y. (Ealing, GB)
Simply outstanding

Words cannot do this watchcase justice. The quality is so high, I am so impressed once again with the products of Lucius Atelier. This watch has to be experienced in person to really see just how good it is!

Ben (Monkton, US)
First Build - Amazing Case and Bracelet!

This is such a well-built product. It looks and feels like a high-end luxury piece. I recommend getting the solid case back to shave an extra 0.6 mm off the profile for a perfect fit on the wrist.