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Seikonaut Watch Case - 40mm

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


  • For a complete watch, select your (1) Dial, (2) Hands and (3) Movement.
  • To have watch assembled, select (4) 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.


From the iconic nautilus and Japanese Seiko comes the hybrid, Seikonaut.

Our own reinterpretation, every part, notches and crevices was redesigned from scratch. Creating a whole new allure and a refinement of the iconic design.

This Seikonaut case comes complete with clear AR sapphire, sapphire caseback, screw down crown and solid brush and polished bracelet. Additionally, it has a water resistant of 200m.

Designed to fit all of our dials (28.5mm) and original NH movements (grey dial holding spacer).

**Please note that assemble watch option will assemble the entire timepiece ready for use and requires 2-5 business days prior to shipping.

For black edition, visit here

Customer Reviews

Based on 42 reviews
Flo (Neuilly-sur-Seine, FR)
Using this mod part for: Seikonaut case
My precious Seikonaut

First, this case is beautiful by itself and perfectly done. Very easy to build, every part is machined well and fit together without the need for any adjustments from me.
Now, let's talk about the service. I pre-ordered the case and misread the estimated delivery date (my fault), so when the case was ready to ship, I was out of my country for a long time. I just send an email asking to keep my order till I came back and very quickly got an answer from Adriel telling there was no problem. I just send a mail when I came back (more than a month later) and the package was send the same day !
To conclude I'll say that this was perfect from start to end ! Product quality, service and quick shipping !

Jorge Fernandez (San Juan, PR)
Using this mod part for: 40mm Lucius Atelier Seikonaut case
High Quality Case

The look of this case is amazing. Fit and finish are superb too. Only reason I'm giving 4 stars is because the crown had to be worked a lot to fit perfectly. Out of the box the crown kept getting stuck in the compressed position. Stem length is crucial for proper fitment. Build shown is Lucius Atelier 40mm Seikonaut case, Namoki mods sakura navy dial, snowflake hands, and regulated NH35.

Muaxayan Saleem
Using this mod part for: Aftermarket seiko
Amazing stuff

I ordered this case for a mod and the goods perfect. The build quality is on par with swiss brands. I really liked the case and loved the way my watch turned out. I will buy more of these cases.

Brad (Sacramento, US)
Excellent quality!

Great design. The proportions work very well.

Alex Smyth (Greenwich, US)
Using this mod part for: Full build from scratch.
Top Tier

I would like to think that I have ordered just about every case quality there is. These cases are definitely as good as they come. From the type of stainless to the finishing, by far the best case I have ever ordered. I have read a few complaints where some would like to have their crown of choice for these cases which I could agree with in some ways but the crown used suits it perfectly fine. Will definitely be wearing this more than my others in the foreseeable future.

Jarryd Fisher (Coventry, GB)
Using this mod part for: Skx007 into a seikonaut

This case is bang on! Looks fantastic, solidly built, bracelet is gorgeous. Hopefully in time it can be a bit thinner, but it's currently one of the top mod cases on the market.

Muhd Nurhakim (Singapore, SG)
Seikonaut mod watch

Bought a seikonaut watch with a snowflake dial and was very satisfied with the outcome. Watch turns out great..really love it!!! And adriel was very nice in accommodating my request..the service was excellent..thanks adriel!! Definitely will purchase more from u guys.. cheers!!

James Brandt (Järfälla Municipality, SE)
GREAT quality watch case!

Super nice, just as described by the pictures seen.

Kristoffer (Ørsta, NO)

Bought the seikonaut with the snowflake dial, i chose the assemble watch option. It just came in today, really happy with the look and feel of the case and bracelet. The watch wears really comfortable and has a heft to it while on the wrist. The snowflake dial looks amazing!

David Braybrook
Using this mod part for: Seikonaut Watch Case
Almost perfect

Stunning Case and Bracelet, let down by sticking crown