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Seiko Alpinist Compass Bearing Function 39.5mm Mens Strap Watch
Ref. SPB121J1
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 £2,900 across 166 Seiko watches in stock.A dark green sunburst dial sits at the heart of this 39.5mm stainless steel case, its surface shifting tone as the viewing angle changes. Cathedral hands and applied hour markers carry LumiBrite luminescence, while the date appears at 3 o'clock beneath a sapphire crystal fitted with a cyclops magnifier and inner anti-reflective coating. The case combines brushed and polished finishing, with a see-through caseback revealing the 6R35 movement. Two crowns define the design: one at 3 o'clock for winding and setting, one at 4 o'clock operating the rotating inner compass bezel. The calibre offers 70 hours of power reserve, a hacking seconds function, and manual winding. A brown calfskin strap with alligator print closes with a three-fold deployant clasp.
- Reference
- SPB121J1
- Brand
- Seiko
- Collection
- Prospex
- Case size
- 39.5mm
- Case thickness
- 13.2mm
- Case material
- Stainless steel
- Case shape
- Round
- Dial
- Green
- Crystal
- Sapphire
- Bezel
- Rotating
- Movement
- Automatic
- Calibre
- 6R35
- Functions
- Date
- Water resistance
- 200m
- Bracelet / strap
- Leather strap
- Strap colour
- Brown
- Clasp
- Three-fold clasp
- Lume
- LumiBrite
- Retailer
- F.Hinds
Additional specifications
- Lug-to-lug
- 46.4mm
- Power reserve
- 70 hours
- Weight
- 87g
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), Back in Stock (3,434), Stainless Steel Watches (2,782), Automatic Watches (1,540), Leather Strap Watches (910), Sports Watches (700) and Dive Watches (503).
Manufacturer’s guarantee
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- 39.5mm suits most wrists
- 46.4mm lug-to-lug keeps the 39.5mm case wearable
- Sapphire crystal, which resists scratching
- 70-hour reserve survives a weekend off the wrist
Worth knowing
- Leather does not suit regular contact with water
Seiko Alpinist Compass Bearing Function alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | SPB121J1 | C0324301604100 | 98A324 |
|---|---|---|---|
| Price | £690 | £695 | £599 |
| Case size | 39.5mm | 41mm | 41mm |
| Water resistance | 200m | 200m | 200m |
| Movement | Automatic | Automatic | Automatic |
| Strap | Leather strap | Leather strap | Fabric strap |
| Power reserve | 70 hours | 80 hours | 60 hours |
| This watch |
|
|
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 70 hours fully wound — enough to sit off the wrist over a weekend and still be running.
Will it fit my wrist?
Lug-to-lug is 46.4mm, which suits wrists from roughly 16cm (6¼ 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, though at 39.5mm it sits in the range that suits anyone.
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.
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