GS 39mm Ultra Thin watch case in polished 316L steel — front view showing the slim bezel and pre-installed sapphire crystal

GS 39mm Ultra Thin watch case — angled view showing brushed lug tops against mirror-polished bevels

GS 39mm Ultra Thin watch case — rear three-quarter view showing the caseback opening and lug undersides

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GS 39mm — Ultra Thin NH34-Ready Watch Case

Name: GS 39mm — Ultra Thin NH34-Ready Watch Case
Brand: Lucius Atelier
SKU: GS39UT/NH.Solid
Price: 120.0 SGD
Availability: InStock

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$120 SGD - $145 SGD

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The GS Dress Case. Faceted Lines, 39mm. Now Ultra Thin.

The GS Watch Case 39mm is the newest addition to our Ultra Thin Edition — and the largest case the line has ever carried. A clean dress case in the Grand Seiko idiom: sharp facets, dial-forward proportions, and surfaces that alternate between linear brushing and mirror polish — bezel top and lug faces brushed, every bevel and flank mirrored, so the case throws a hard line of light exactly where the two meet.

Getting a 39mm GS into Ultra Thin architecture meant re-engineering every internal dimension to compress case height without giving up structure. The result is 10.95mm total in solid 316L stainless steel — a full 1.85mm slimmer than the GS 39mm it replaces, with none of the diameter given back.

Then the twist. Despite the slim profile, this case is fully NH34-ready — it takes a GMT movement. Fitting a GMT caliber into a sub-11mm case is an extraordinary engineering feat, and it means you can build something genuinely uncommon: a large, thin, faceted GMT.

Sapphire pre-installed. Ready to assemble.
The double-domed sapphire crystal is the trickiest part of a slim build to seat — so we've done it for you. It ships pre-installed and aligned at our workshop, no crystal-pressing, no fitment guesswork. Our biggest Ultra Thin case, ready for your dial.

Our largest Ultra Thin — 39mm.
Case diameter 39mm, lug-to-lug 46.5mm, lug width 20mm. The Ultra Thin Edition used to stop at 38mm; this is the case for anyone who wanted the slim architecture with real wrist presence. The line now runs 33mm to 39mm.

Genuinely thin.
10.95mm total with the solid caseback, including crystal. The engineering behind that number: a standard NH movement is 7.59mm tall on its own — the NH34 GMT, 7.99mm. That leaves barely 3mm for the crystal, caseback floor, walls and hand clearance combined. The NH is a big movement; compressing one into this profile is the whole challenge.

GMT-capable — the uncommon build.
Fully NH34-ready. Most slim cases can't take a GMT movement; this one does, without giving up the profile. A thin 39mm faceted GMT is a build few modders can make.

Half brushed, half mirror.
The finishing is where a GS case is won or lost. The bezel top face and the lug surfaces are linear-brushed; the bevels, flanks and corner facets are mirror-polished. Every edge between the two is a crisp line, not a fade — which is exactly why the case reads sharp in the light. Our GS Bracelet is finished the same way, so the two read as one piece.

Caseback	Total Thickness	Water Resistance	Best for
Solid · HEADLINE BUILD	10.95mm	100m / 10 ATM	The thinnest profile — daily and formal wear
Sapphire	11.75mm	100m / 10 ATM	Movement display — show off the rotor

The solid caseback is the headline build — this is the case at its slimmest. The sapphire caseback adds 0.8mm in exchange for a view of the NH movement.

The GS case family — find your size

Case	Diameter	Thickness	Character
GS 39mm Ultra Thin · YOU'RE VIEWING THIS	39mm	10.95mm	Faceted dress case, largest — NH34 GMT-ready
62GS 36mm Ultra Thin	36mm	11.3mm	Bezel-less GS, crown at 4 — NH34 GMT-ready
GS Diver 36mm	36mm	12.5mm	Dive-styled GS, 200m rated — NH34 GMT-ready
GS 36mm v2	36mm	12.8mm	Faceted dress case, classic mid-size

All four share the GS design language — 316L steel, a double-domed sapphire pre-installed, 28.5mm dials, an SKX013 chapter ring, and a 20mm bracelet or strap. Thickness shown is with the solid caseback; a sapphire caseback adds 0.5–0.9mm. The GS 39mm and 62GS 36mm are built on our Ultra Thin architecture — and the GS 36mm v2 is the one case here that is not NH34 GMT-ready.

Heads up — sold separately

Crown. The crown shown in product photos is for visual reference only. Crowns must be selected above. Browse compatible crowns .

Chapter ring. This case requires a SKX013-spec chapter ring to seat the dial correctly — without it, the dial sits too low and hands won't clear. The case fits both normal and ultra thin chapter rings; the choice depends on your dial, not the case. If your dial has applied (raised) indices, choose ultra thin for clearance. If flat-printed, either works. When in doubt, ultra thin is the safer default. Browse compatible chapter rings .

For experienced modders only — TYPE M movements only

This case fits TYPE M versions of NH34, NH35, NH36, NH38, NH70, NH71, NH72 only. TYPE L will NOT fit. Due to tight clearance between hands and sapphire, this case is recommended only for professional watchmakers and experienced modders.

NH34 / GMT builds: for optimal second-hand clearance, the second hand must be under 12mm in length — or use a second-hand cap. Confirm before assembly.

Specs
Build Guide
What's Included
How To Mod

Dimensions
1. Case Diameter 39mm
2. Case Thickness 10.95mm (Solid Caseback) / 11.75mm (Sapphire Caseback)
3. Lug to Lug 46.5mm
4. Lug Width 20mm
Materials & Finish
1. Quality Swiss Production Quality, ISO 9001 Certified
2. Case Material 316L Stainless Steel
3. Case Finishing Alternating linear brushing and mirror polish — brushed bezel top and lug surfaces, mirror-polished bevels, flanks and corner facets
4. Bezel Slim, with a linear-brushed top face
5. Crystal Double-domed sapphire with clear anti-reflective coating
6. Crystal Size 29.5mm x 1.8mm x 1mm
7. Crown Screw-down, SKX-style compatible
Compatibility
1. Movements TYPE M: NH34, NH35, NH36, NH38, NH70, NH71, NH72
2. Dials 28.5mm
3. Chapter Rings SKX013-spec (required, sold separately)
4. Hands NH movement compatible
5. Crowns SKX-style
6. Bracelets & Straps 20mm lug — GS Bracelet 20/16mm recommended for this build
Water Resistance
1. Solid & Sapphire Caseback 100m / 10 ATM
New to Seiko modding? Here's everything you'll need for a complete, functioning watch — in the order you'd actually assemble it.

What's already in this purchase:

The case body with pre-installed double-domed sapphire crystal, and your chosen caseback. That's the foundation. Everything below is what you'll add to make a wrist-ready watch.

The 5 parts you'll need for a complete watch:
1. Chapter ring — required first. The chapter ring seats the dial at the correct height; without it, the dial sits too low and the hands won't clear.
  (SKX013-spec — sold on a separate page. See the "sold separately" panel above for normal vs ultra thin guidance.)
  Browse compatible chapter rings
2. Crown — SKX-style options. Pick a style that matches the watch's character.
  (Required to add to cart. Selected from the dropdown above on this page.)
  Browse compatible crowns
3. Dial (28.5mm) — the face of the watch. The biggest aesthetic choice you'll make. Match it to your chosen movement (date / day+date / GMT / no-date dial).
4. Hands — paired with your dial. Most modders match lume colour across both hands and dial markers (BGW9 white-blue, C3 green, etc.). For NH34 GMT builds, you'll also need a GMT hand.
5. Movement — NH34 (GMT), NH35 (date), NH36 (day+date), NH38 (no date), or source your own. The movement is the engine of the watch.
Optional finishing touches:
1. Bracelet or strap (20mm lug) — we recommend our GS Bracelet 20/16mm , finished with the same alternating brushed and polished surfaces as the case, plus custom shell cordovan / full-grain cowhide leather straps.
2. Decorated bridge + rotor (only visible with sapphire caseback) — replace the stock NH movement bridge and rotor with our Côtes de Genève decorated set, viewable through the sapphire caseback. Note: our bridges fit only our rotors (not OEM Seiko rotors), so they're chosen as a pair. Recommended for experienced modders only — or tick Assemble Watch below and we'll handle it.
Want it built for you?

Tick the Assemble Watch (+SGD $50) option above on this page and we'll handle the full build in our Singapore workshop — case fitting, movement seating, crown alignment, caseback press, function check, and decorated bridge + rotor installation if you've added those.

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 Body (with pre-installed double-domed sapphire crystal)
2. 1x NH Caseback (Solid or Sapphire, per selection)
All photos of watches with modification parts are for illustration purposes only and are not included with the case purchase.

Which movements fit the GS 39mm Ultra Thin case?

Seiko NH movements only, and TYPE M versions specifically: NH34, NH35, NH36, NH38, NH70, NH71 and NH72. TYPE L will not fit. Swiss ETA and Sellita movements are not supported on this case. It is NH34 GMT-ready, so a true GMT build is on the table — for those, keep the second hand under 12mm or use a second-hand cap. Because clearance between the hands and the sapphire is tight, this case is recommended for experienced modders. The dial, hands, movement and an SKX013 chapter ring are all chosen separately.

Can this case really take a GMT movement?

Yes — it is fully NH34-ready, and that is the uncommon part. The NH34 GMT stands 7.99mm tall against 7.59mm for a standard NH, while this case is 10.95mm in total with the solid caseback — so the crystal, caseback floor, case walls and hand clearance share barely 3mm between them. Most cases this slim cannot take a GMT at all. Two things to get right: use a GMT / NH34-specific dial, because the NH34 needs the larger centre hole and a standard NH35 dial will not fit; and keep the second hand under 12mm or fit a second-hand cap. You will also need a 24-hour GMT hand.

Which caseback should I choose for the GS 39mm Ultra Thin?

Both casebacks take the same Seiko NH movements, so the choice is profile versus view. Solid is the slimmest at 10.95mm total; the sapphire (exhibition) caseback is 11.75mm and lets you see the movement. Both are rated 100m / 10 ATM. If you are adding a decorated bridge and rotor, pick sapphire — it is the only way you will ever see them.

How is this different from the GS 39mm v2?

Same 39mm faceted GS silhouette, rebuilt on our Ultra Thin architecture. The headline is thickness: 10.95mm with the solid caseback against the v2's 12.8mm — 1.85mm slimmer at the same diameter. Two other differences matter before you buy. The v2 took Swiss ETA and Sellita movements through a selectable caseback; this case is Seiko NH only, and TYPE M versions specifically. And water resistance is 100m / 10 ATM here against 200m on the v2 — that is the trade for the slimmer case. The v2 is being discontinued, and this replaces it.

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.

Do I need to remove the sapphire crystal to install the chapter ring?

No — and that's the whole point of us pre-installing the sapphire for you. The chapter ring sits on top of the dial inside the case, not under the crystal, so the crystal stays where it is throughout the build. (If you ever do need to remove the sapphire — for example, to replace it — that's a workshop job we handle for you, not an at-home step.)

Should I choose the normal or the ultra thin chapter ring?

The choice depends on your dial, not the case — both sizes fit every Ultra Thin Edition case. If your dial has applied (raised) indices, the ultra thin chapter ring is the better choice because its slimmer profile gives the indices clearance instead of resting on top of them. If your dial is flat-printed (no applied markers), either size works. When in doubt, the ultra thin chapter ring is the safer default because it works with both dial types.

What is an SKX013 chapter ring and why does it matter?

A specific size and spec used by Seiko in the SKX013 (discontinued 2019). The LA smaller-case lineup all uses this same spec, which means dozens of chapter ring designs work across every smaller case in the catalogue.

Will SKX007 dials fit?

Any 28.5mm dial will fit. Stock SKX007 dials may seat differently because the original SKX007 has a 4 o'clock crown position with offset dial feet, while Ultra Thin Edition cases are designed for 3 o'clock dial feet.

Does this case need a chapter ring?

Yes — every Ultra Thin Edition case requires an SKX013-spec chapter ring, sold separately. The chapter ring seats the dial at the correct height; without it, the dial drops and the hands will not clear properly.