GS 39mm — Ultra Thin NH34-Ready Watch Case

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 Case Diameter 39mm Case Thickness 10.95mm (Solid Caseback) / 11.75mm (Sapphire Caseback) Lug to Lug 46.5mm Lug Width 20mm Materials & Finish Quality Swiss Production Quality, ISO 9001 Certified Case Material 316L Stainless Steel Case Finishing Alternating linear brushing and mirror polish — brushed bezel top and lug surfaces, mirror-polished bevels, flanks and corner facets Bezel Slim, with a linear-brushed top face Crystal Double-domed sapphire with clear anti-reflective coating Crystal Size 29.5mm x 1.8mm x 1mm Crown Screw-down, SKX-style compatible Compatibility Movements TYPE M: NH34, NH35, NH36, NH38, NH70, NH71, NH72 Dials 28.5mm Chapter Rings SKX013-spec (required, sold separately) Hands NH movement compatible Crowns SKX-style Bracelets & Straps 20mm lug — GS Bracelet 20/16mm recommended for this build Water Resistance 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: 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 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 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). 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. 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: 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. 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. 1x Watch Case Body (with pre-installed double-domed sapphire crystal) 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. A Complete Guide On How To Mod Your SEIKO Watch Dial And Hands (Photos & Video) Fitting dials with four dial legs Seiko Modding: The Complete Build Guide (2026)