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Seiko 5 Sports SRPD51K2 Men's Watch – 42.5mm Blue Dial Nylon
Ref. SRPD51K2
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The cushion-shaped case gives this automatic a slightly retro, sport-oriented silhouette that sits comfortably on the wrist without overwhelming it. At 42.5mm it occupies the middle ground between understated and purposeful. The blue dial is the centrepiece, paired with a nylon strap that keeps the overall feel casual and lightweight. Seiko's 5 Sports line has always leaned toward legibility and everyday robustness, and this reference follows that tradition with a straightforward layout suited to regular wear.
- Reference
- SRPD51K2
- Brand
- Seiko
- Case size
- 42.5mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Blue
- Crystal
- Hardlex
- Bezel
- Unidirectional rotating
- Movement
- Automatic
- Calibre
- 4R36
- Functions
- Date
- Water resistance
- 100m
- Bracelet / strap
- Fabric strap
- Strap colour
- Blue
- Clasp
- Buckle
- Lume
- Luminous
- Retailer
- Watch Enclave
Additional specifications
- 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.
Also in 4 collections
This watch appears in Stainless Steel Watches (2,890), Automatic Watches (1,599), Blue Dial Watches (789) and Automatic Watches Under £500 (320).
Temporarily out of stock
Watch Enclave is not currently taking orders for this reference. Last listed as available on 15 August 2026. Stock is checked nightly and this page updates when it returns.
What the specifications mean
A mechanical watch for everyday wear.
Strengths
- 100m water resistance covers swimming and watersports
- Luminous hands and markers for low light
- Sits in the lower half of Seiko's range as we list it
Seiko 5 Sports SRPD51K2 alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | SRPD51K2 | R8821108036 | RGB10007/05 |
|---|---|---|---|
| Price | £299 | £299 | £299 |
| Case size | 42.5mm | 43mm | 43mm |
| Water resistance | 100m | 100m | 100m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Fabric strap | Leather strap | Stainless steel bracelet |
| Power reserve | 41 hours | — | — |
| This watch | Closely matched | Closely matched |
Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 100m it is rated for swimming and snorkelling, though not for diving.
Water resistance explainedWill the glass scratch?
It resists most everyday knocks. Hardlex is a hardened mineral glass — tougher than standard mineral, softer than sapphire.
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 41 hours fully wound — enough to survive a night off the wrist, but not a full weekend.
Is it a men's or women's watch?
Listed as men's.
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