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Seiko Prospex Divers GMT 'Marine Green' 42mm Mens Watch - 1968 Modern Re-interpretation
Ref. SPB381J1
Sits in Seiko’s upper tier here — more premium than three quarters of the Seiko watches we list, which start at £110.
Price range £110 to £3,550 across 168 Seiko watches in stock.The SPB381J1 belongs to a trio of watches Seiko built around a single milestone: the introduction of the 6R54, their first mechanical GMT calibre in a diver's watch. The anchor point for the design is the 1968 one-piece diver, Japan's first hi-beat diver and the watch that set the direction for everything Seiko built in the category afterwards. Returning to that case shape to house a genuinely new movement rather than a cosmetic refresh gives this watch a clearer reason to exist than most anniversary pieces manage. The 6R54 earns attention beyond its GMT function. The home-time hand adjusts independently in one-hour steps without disturbing the running hands — a small thing that matters on a travel watch — and a 24-hour scale on the rehaut keeps the second timezone readable without cluttering the marine green dial. At 12.9mm thick for a 200m-rated diver with GMT complication, the case sits lower than the rating might suggest, and the 42mm footprint with its contoured edges keeps 176g of steel from feeling punishing over a full day. The ceramic bezel matches the dial colour and, by reviewer consensus, turns with the kind of resistance that feels deliberate without being effortful.
- Reference
- SPB381J1
- Brand
- Seiko
- Collection
- Prospex
- Case size
- 42mm
- Case thickness
- 12.9mm
- Lug width
- 20mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Green
- Crystal
- Sapphire
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- 6R54
- Functions
- GMT, Date
- Water resistance
- 200m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Three-fold clasp
- Lume
- LumiBrite
- Retailer
- Goldsmiths
Additional specifications
- Lug-to-lug
- 48.6mm
- Power reserve
- 72 hours
- Weight
- 176g
Learn more about Seiko
Kintaro Hattori opened a watch and clock shop in Tokyo in 1881, aged twenty-one, and began manufacturing under the name Seikosha — roughly, house of exquisite workmanship — in 1892. The Seiko name appeared on watches from 1924.
The company's significance is that it broke the Swiss monopoly twice. First on precision: Seiko was appointed official timekeeper of the 1964 Tokyo Olympics and built the quartz chronometers and printing timers to do it, and in the 1960s its movements placed highly at the Neuchâtel and Geneva observatory trials against the best Swiss houses.
Then on technology. On Christmas Day 1969 Seiko released the Astron, the world's first quartz wristwatch, accurate to five seconds a month where mechanical watches managed that per day. The consequences for Switzerland were catastrophic — employment in the Swiss industry fell by roughly two-thirds over the following decade. Seiko deliberately did not enforce its quartz patents, allowing the technology to spread.
The same year it produced the 6139, among the first automatic chronographs, and it has since introduced Kinetic, Spring Drive — a hybrid regulating a mechanical mainspring electronically, giving a perfectly gliding seconds hand — and its own dive and field lines.
Seiko remains fully vertically integrated, making its own hairsprings, quartz crystals, and even the Zaratsu-polished cases, at price points from under a hundred pounds upward.
- 1881
- Kintaro Hattori opens his Tokyo shop.
- 1924
- The first watches carry the Seiko name.
- 1964
- Official timekeeper of the Tokyo Olympics.
- 1969
- The Astron becomes the first quartz wristwatch.
- 1999
- Spring Drive enters production.
Also in 7 collections
This watch appears in the Seiko Prospex range (32), Stainless Steel Watches (2,833), Automatic Watches (1,417), Sports Watches (667), Dive Watches (486), Green Dial Watches (392) and GMT Watches (208).
Temporarily out of stock
Goldsmiths is not currently taking orders for this reference. Last listed as available on 23 August 2026. Stock is checked nightly and this page updates when it returns.
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- 48.6mm lug-to-lug keeps the 42mm case wearable
- Sapphire crystal, which resists scratching
- 72-hour reserve survives a weekend off the wrist
- Luminous hands and markers for low light
Seiko Prospex Divers GMT 'Marine alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | SPB381J1 | 799.10.351.10 | ZO9270 |
|---|---|---|---|
| Price | £1,400 | £1,190 | £1,399 |
| Case size | 42mm | 42mm | 40mm |
| Water resistance | 200m | 200m | 200m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | Stainless steel bracelet | Rubber strap |
| Power reserve | 72 hours | 38 hours | 44 hours |
| This watch |
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Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 200m it is rated for swimming, snorkelling and recreational diving.
Water resistance explainedWill the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Sapphire, mineral and acrylic comparedDoes it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
Quartz, automatic and solar comparedHow long does it run for when it's not worn?
About 72 hours fully wound — enough to sit off the wrist over a weekend and still be running.
What size strap does it take?
20mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.
Will it fit my wrist?
Lug-to-lug is 48.6mm, which suits wrists from roughly 16.5cm (6½ inches) upward.
Lug-to-lug decides fit more than case diameter does.
How to size a watch to your wristIs it a men's or women's watch?
Listed as men's.
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