{"product_id":"seikonaut-40mm-case","title":"Seikonaut 40mm Case — Ultra-Thin Nautilus-Style Seiko Mod Case","description":"\u003cp\u003eThe Seikonaut 40mm is one of the thinnest Nautilus-style Seiko mod cases available — just 9.95 mm at the solid caseback. CNC-machined from 316L stainless steel with brushed and polished surface finishing, this 40 mm case features an integrated-lug silhouette inspired by the iconic Nautilus shape, available in six finishes (Silver, Black, Gold, Rose Gold, Two-Tone Gold, Gunmetal). The included sapphire crystal comes with your choice of clear or blue AR coating, and the screw-down crown delivers 50 m water resistance. Compatible with NH35, NH36, NH38, NH70, NH71, and NH72 movements using 30.8 mm dials — read on for full specs, compatibility details, and finish guidance.\u003c\/p\u003e\n\u003ch2\u003eAvailable in 6 finishes\u003c\/h2\u003e\n\u003cp\u003eJump to: \u003ca href=\"#silver\"\u003eSilver\u003c\/a\u003e · \u003ca href=\"#black\"\u003eBlack\u003c\/a\u003e · \u003ca href=\"#gold\"\u003eGold\u003c\/a\u003e · \u003ca href=\"#rose-gold\"\u003eRose Gold\u003c\/a\u003e · \u003ca href=\"#two-tone-gold\"\u003eTwo-Tone Gold\u003c\/a\u003e · \u003ca href=\"#gunmetal\"\u003eGunmetal\u003c\/a\u003e\u003c\/p\u003e\n\n\u003ch3 id=\"silver\"\u003eSilver — brushed stainless with polished accents\u003c\/h3\u003e\n\u003cp\u003eThe cleanest, most versatile finish. Brushed 316L surfaces with polished bevel transitions catch light without showing wear. The all-purpose choice that pairs with any dial and any strap.\u003c\/p\u003e\n\n\u003ch3 id=\"black\"\u003eBlack — full PVD-coated stealth finish\u003c\/h3\u003e\n\u003cp\u003eA full physical-vapor-deposition coating across the case body, bracelet, and caseback. The matte tonality reads dressy-stealth in daylight and disappears entirely in low light. Pairs strongly with skeleton dials and dark-toned hands.\u003c\/p\u003e\n\n\u003ch3 id=\"gold\"\u003eGold — warm yellow champagne tone\u003c\/h3\u003e\n\u003cp\u003eYellow-gold PVD with a champagne warmth in the brushed surfaces. The dressiest of the warm-tone finishes; pairs traditionally with cream or champagne dials and brown leather, more boldly with deep blue or black-skeleton dials.\u003c\/p\u003e\n\n\u003ch3 id=\"rose-gold\"\u003eRose Gold — soft pink-gold dress tone\u003c\/h3\u003e\n\u003cp\u003ePink-gold PVD applied at lower colour-saturation than the yellow variant — reads warm and understated, the dressiest of the six finishes. Pairs especially well with white, ivory, or chocolate dials.\u003c\/p\u003e\n\n\u003ch3 id=\"two-tone-gold\"\u003eTwo-Tone Gold — brushed steel with polished gold accents\u003c\/h3\u003e\n\u003cp\u003eA duo finish — brushed silver case body with polished gold bezel, crown, and centre bracelet links. Bridges the silver and gold options for builds that don't commit to one tone. Often called a champagne or bi-colour configuration.\u003c\/p\u003e\n\n\u003ch3 id=\"gunmetal\"\u003eGunmetal — deep cool-grey with smoky finish\u003c\/h3\u003e\n\u003cp\u003eA cooler tonal cousin of black PVD — deeper than steel, lighter than full black, with a faint warm-grey undertone. The most unusual finish; pairs distinctively with brushed-steel dials or earth-toned leather.\u003c\/p\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eDiameter\u003c\/td\u003e\n\u003ctd\u003e40 mm (10H–4H) — 38 mm (12H–6H)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eThickness\u003c\/td\u003e\n\u003ctd\u003e9.95 mm (solid caseback) \/ 10.3 mm (exhibition caseback)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003e316L Stainless Steel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFinish\u003c\/td\u003e\n\u003ctd\u003eBrushed with polished accents\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCrystal\u003c\/td\u003e\n\u003ctd\u003eSapphire (clear or blue AR coating)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWater Resistance\u003c\/td\u003e\n\u003ctd\u003e50 m\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDial Fit\u003c\/td\u003e\n\u003ctd\u003e30.8 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCrown\u003c\/td\u003e\n\u003ctd\u003eScrew-down, included\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch2\u003eCompatibility\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eMovements:\u003c\/strong\u003e NH35, NH36, NH38, NH70, NH71, NH72 — all standard Seiko NH-family automatics fit without modification. The crown stem must be cut to length during installation.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDials:\u003c\/strong\u003e 30.8 mm dials only. This case does not accept 28.5 mm dials without a spacer ring. Pair it with our \u003ca href=\"\/en-ca\/products\/nautilus-skeleton-dial-30-8mm\"\u003eNautilus Skeleton Dial 30.8mm\u003c\/a\u003e for a skeleton build, or any other 30.8 mm dial designed for the NH35-family.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eBracelet:\u003c\/strong\u003e Stainless steel Seikonaut integrated bracelet included with the case. Standard spring bar attachment at the lugs, so you can swap to a rubber or leather strap if you prefer.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eNot compatible:\u003c\/strong\u003e 7S26 and 7S36 movements use a different stem height and are not recommended for this case.\u003c\/p\u003e\n\u003ch3\u003eWhat's Included\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eSeikonaut 40mm case body in your selected finish (316L stainless steel)\u003c\/li\u003e\n\u003cli\u003eSapphire crystal in your selected AR coating (clear or blue)\u003c\/li\u003e\n\u003cli\u003eCaseback in your selected configuration (solid or exhibition)\u003c\/li\u003e\n\u003cli\u003eScrew-down crown\u003c\/li\u003e\n\u003cli\u003eStainless steel Seikonaut integrated bracelet\u003c\/li\u003e\n\u003cli\u003eGaskets (pre-installed)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cem\u003eTools are not included. You will need a case opener, hand press, stem cutter, and movement holder for assembly.\u003c\/em\u003e\u003c\/p\u003e\n\u003ch2\u003eDesigned by Nomods\u003c\/h2\u003e\n\u003cp\u003eThe Seikonaut is our take on the ultra-thin Nautilus-style case for Seiko mods. The 9.95 mm solid-caseback profile is the thinnest configuration we make, designed for builders who want the Nautilus integrated-lug silhouette in a dress-watch profile. The exhibition caseback adds 0.35 mm for skeleton builds where you want the movement visible. Every case is individually checked for brushing consistency, edge sharpness, and crystal seating before shipping.\u003c\/p\u003e\n\u003ch2\u003eComplete Your Build\u003c\/h2\u003e\n\u003cp\u003ePair the Seikonaut 40mm case with these compatible components:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"\/en-ca\/products\/nh35-movement\"\u003eNH35 Movement\u003c\/a\u003e — the standard automatic movement for this case\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/en-ca\/products\/nh72-skeleton-movement\"\u003eNH72 Skeleton Movement\u003c\/a\u003e — for skeleton builds with the exhibition caseback\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"\/en-ca\/products\/royal-oak-hands-v2-silver\"\u003eSilver V2 Hands\u003c\/a\u003e — Nautilus-compatible hands in brushed silver\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eBrowse Collection\u003c\/h2\u003e\n\u003cp\u003e\u003ca href=\"\/en-ca\/collections\/nautilus-style-parts\"\u003eNautilus Style Mod Parts\u003c\/a\u003e — \u003ca href=\"\/en-ca\/collections\/seiko-mod-cases\"\u003eAll Seiko Mod Cases\u003c\/a\u003e — \u003ca href=\"\/en-ca\/collections\/seiko-nautilus\"\u003eAll Seiko Nautilus Mods\u003c\/a\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cem\u003eNomods is an independent brand specializing in Seiko-compatible watch modifications. We are not affiliated with, endorsed by, or connected to Seiko, Rolex, Audemars Piguet, Patek Philippe, or any other watch brand mentioned on this site. All brand names and trademarks are the property of their respective owners and are used solely for descriptive and comparative purposes.\u003c\/em\u003e\u003c\/p\u003e\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\/\",\n  \"@type\": \"Product\",\n  \"@id\": \"https:\/\/nomods.co\/products\/seikonaut-40mm-case#product\",\n  \"name\": \"Seikonaut 40mm Case — Ultra-Thin Nautilus-Style Seiko Mod Case\",\n  \"description\": \"Ultra-thin 9.95mm Nautilus-style Seiko mod case in six finishes (Silver, Black, Gold, Rose Gold, Two-Tone Gold, Gunmetal). CNC-machined 316L stainless steel, sapphire crystal with clear or blue AR coating, screw-down crown, 50m water resistance. 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