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Seiko Diver's 'Samurai' 43.8mm Mens Watch
Ref. SRPF03K1
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Stepping up in the same colour and case shape
The Samurai name is earned not through marketing but through the case itself — those aggressively chamfered lugs, cut at sharp angles and faceted like armour plate, give the watch a silhouette unlike anything else in the Prospex line. The waffle-textured dial and matching crown push the industrial character further, and at 43.8mm the whole thing looks as though it should wear large. It does not: a lug-to-lug of 48.7mm, with the lugs curving sharply down toward the wrist, means it sits closer and flatter than the diameter suggests, and fits wrists that most watches of this footprint would dwarf. The 4R35 inside is Seiko's dependable workhorse — hand-windable, hacking, and proven across years of production. It is not the movement chosen for the top of the Prospex range, but it keeps time reliably, and for a watch worn into water regularly, that straightforward durability is a reasonable trade. The clasp includes a fold-out wetsuit extension, which is a small detail that confirms this watch is meant to be used rather than kept respectable.
- Reference
- SRPF03K1
- Brand
- Seiko
- Collection
- ProspexCase Size: 43
- Case size
- 43.8mm
- Case thickness
- 13.4mm
- Lug width
- 22mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Black
- Crystal
- Hardlex
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- 4R35
- Functions
- Date
- Water resistance
- 200m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Three-fold clasp
- Lume
- LumiBrite
- Retailer
- F.Hinds
Additional specifications
- Lug-to-lug
- 48.7mm
- Power reserve
- 41 hours
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.
Manufacturer’s guarantee
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What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- 48.7mm lug-to-lug keeps the 43.8mm case wearable
- Luminous hands and markers for low light
Worth knowing
- 43.8mm sits at the larger end
Compare alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | SRPF03K1 |  RA-AA0003R39B |  GM-B2100BD-1AER |
|---|---|---|---|
| Price | £399 | £385 | £549 |
| Case size | 43.8mm | 41.8mm | 44mm |
| Water resistance | 200m | 200m | 200m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Stainless steel bracelet | Stainless steel bracelet | Stainless steel bracelet |
| Power reserve | 41 hours | 40 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.
Will the glass scratch?
It resists most everyday knocks. Hardlex is a hardened mineral glass — tougher than standard mineral, softer than sapphire.
Does it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
How long does it run for when it's not worn?
About 41 hours fully wound — enough to survive a night off the wrist, but not a full weekend.
What size strap does it take?
22mm. 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 48.7mm, which suits wrists from roughly 16.5cm (6½ inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as men's.
Cheapest place to buy
Both F.Hinds and Goldsmiths list it at £399, so choose on delivery and warranty rather than price.
Who are F.Hinds?
F.Hinds has been run by the same family since 1856 and is now in its fifth generation, with more than 115 shops across England and Wales. They are a member of the Responsible Jewellery Council and an Authorised Diamond Dealer.
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