Kensington Watches
Seiko Alpinist Compass Bearing Function 39.5mm Mens Strap Watch

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Seiko

Seiko Alpinist Compass Bearing Function 39.5mm Mens Strap Watch

Ref. SPB121J1

Among our 166 Seiko watchesThis watch£690
Premium

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.

All Seiko watches

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
Best forDivingSwimmingEveryday wearFormal wear

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.

Alpinist Compass Bearing Function 39.5mm Mens Strap Watch compared with 2 alternatives from other brands
SpecificationThis watchAlpinist Compass Bearing Function 39.5mm Mens Strap WatchSPB121J1CertinaDS Action Day-Date Powermatic 80 41mm Mens WatchC0324301604100BulovaArchive Series 98A324 MIL-SHIPS Green Watch - Special Edition - W0937398A324
Price£690£695£599
Case size39.5mm41mm41mm
Water resistance200m200m200m
MovementAutomaticAutomaticAutomatic
StrapLeather strapLeather strapFabric strap
Power reserve70 hours80 hours60 hours
This watch
  • Wears larger
  • Costs less
  • Wears larger

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 explained

Will the glass scratch?

Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.

Sapphire, mineral and acrylic compared

Does 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 compared

How 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 wrist

Is 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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