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Seiko Prospex SFJ005P1 'Khaki Stripe' Speedtimer Watch - Limited Edition - W24185
Ref. SFJ005P1
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The 8A50 was built to mark forty years since Seiko produced Japan's first analogue quartz chronograph, and the brief it was given shows in what sits beneath this dial. Rather than sharing a single motor across the whole chronograph mechanism, the movement places an independent micro-motor behind each sub-dial hand — the architecture that allows it to time elapsed seconds to a hundredth of a second with genuine accuracy rather than interpolated display. Solar charging removes the need for routine battery work, and a six-month reserve means the watch can sit unworn through a long stretch without losing its charge or its time. The brown dial reads as a deliberate nod to the analogue instrumentation panels of 1960s competition cars — warm, slightly earthy against the steel case, with the four-register layout reinforcing the purposeful, dashboard quality. At 42mm across and 48.3mm lug to lug it sits well within contemporary proportions, and 12.9mm of thickness is modest enough for a solar chronograph with this level of mechanism density. The bracelet adjusts through a conventional pin system, so dialling in the fit is straightforward without tools.
- Reference
- SFJ005P1
- Brand
- Seiko
- Collection
- Speedtimer
- Case size
- 42mm
- Case thickness
- 12.9mm
- Lug width
- 20mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Brown
- Crystal
- Sapphire
- Movement
- Solar
- Calibre
- 8A50
- Functions
- Chronograph, Solar powered
- Water resistance
- 100m
- Bracelet / strap
- Stainless steel bracelet
- Strap colour
- Silver
- Clasp
- Three-fold clasp
- Lume
- Luminous
- Retailer
- F.Hinds
Additional specifications
- Lug-to-lug
- 48.3mm
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
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.
Will the glass scratch?
Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.
Does it need a battery?
No. It charges from light, and the cell behind that is designed to last a decade or more.
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 48.3mm, 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
F.Hinds is the only UK retailer we track stocking this reference, so there is nothing to compare it against today.
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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