Seiko Prospex Alpinist SPB121J1 Review

The Seiko Prospex Alpinist SPB121J1 with a green dial, compass, and brown leather strap, is without a minute’s hesitation one of Seiko’s classic watches within its range of automatic watches. The Seiko Alpinist has been with us since 1961, and since then, the brand has released numerous versions with minor differences.

Many people like the old model, the Seiko SARB017 (a classic) with caliber 6R15 and no magnifying glass in the date window. The issue of putting the cyclops in the position of the date window is quite controversial.

We have tested the latest version, the Alpinist SPB121, with a green dial and gold-colored numbers and indices, one of the most beautiful watches from the Japanese brand in recent years.

You can also try the SPB117 models with a black dial + metal strap and the SPB119 with a white dial and black leather strap.

Below I will tell you in detail all its functionalities, design, and manufacturing.

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Seiko Prospex Alpinist SPB121J1: features and design

  • Steel case and leather strap
  • No. of jewels: 24
  • 39.5mm diameter
  • Thickness: 13.2mm
  • 20mm strap
  • Water resistance of 20 ATM (200 meters)
  • Sapphire crystal with anti-reflective coating on the inner surface
  • Strap with three-fold closure with button release
  • Stop the second function
  • Lumibrite on hands and indices
  • Accuracy: +25 to -15 seconds per day
  • 70-hour power reserve
  • 87 grams of weight

The watch you see in the photos is the Seiko Prospex Alpinist with a magnifying glass and caliber 6R35. The 6R35 caliber is an update to the 6R15. It still runs at 21,600 BPH and has the manual winding capability, but there is an increase in jewels to 24 and a power reserve of 70 hours from 50 hours on previous versions. Spectacular!

It shows that it is a classic… you fall in love from the first moment you see it. And it even has an interesting story to tell: Seiko’s inspiration to create this marvel came from “Yama-Otoko“, which means “mountain men” in Japanese, and this is the purpose of the watch.

Being a resistant and perfect model to take you on an adventure, hiking, traveling, putting in the water…

The sphere is made of very resistant sapphire crystal, and it has a small magnifying glass that many dislike, but that comes in handy to see the day well. 

The watch offers great legibility in all kinds of situations, specifically when the sun shines directly on it. Is beautiful. It’s a completely green dial, and its hands, indices, and Arabic numerals are in gold.

More cool stuff? The most striking feature of this watch is that it has a crown at 3 o’clock to control the operation of the watch, and another crown at 4 o’clock that moves an internal rotating bezel that acts as a compass (on the dial, on the outside we can see the marks with the cardinal points and the degrees, which will rotate).

It is an off-road and elegant watch that you can take anywhere without feeling that you are going to wear it down.

The slightly polished steel case has a diameter of 39.5 mm, not including the crown (it is relatively small), and 41 mm, including the crown. It is not too thick at 13mm thick.

Probably the only thing that can hold you back in this version is the cyclops-like magnifying glass above the date window. You may or may not like it, but it is useful for a quick glance at the date… especially if you are older and already have vision problems.

In addition, it is water resistant up to 200M, although it is better not to mess with it and the leather strap that is included. You’ll have to change it to do it.

The LumiBrite with the three hands and the dots at each hour is quite bright and very comfortable to wear at night. The contrast between the green background and the gold numbers is tremendous:

On the transparent back, you will be able to admire the automatic mechanism. A great addition.

Seiko Prospex Alpinist SPB121J1: Strap and how it fits on the wrist

My wrist is 18cm, so you can get an idea of ​​how it will fit on you. It is really comfortable. You can even leave it on at night…

Seiko Prospex Alpinist SPB121J1 Review

The vintage look of the watch is completed by the alligator-style brown leather strap with a really secure closure. It’s the perfect watch to take to the countryside for a hike. It is a three-fold closure strap with a button release. Everything gives a feeling of tremendous robustness.

Operation of the Seiko Prospex Alpinist SPB121J1

Well, the truth is that it works with tremendous precision, at least in our model. It has the same caliber as the Seiko Prospex Diver SPB143J1.

This model is an automatic mechanical watch with a manual winding mechanism  (the spring will not break by turning the crown any further). So it works by winding it yourself or with the flick of your wrist. It has a power reserve of up to 70 hours, so it’s not bad at all. You can take it off for a couple of days without losing the time setting. 

You know. Do not set the date between 9:00 pm and 1:00 am. If the hour hand is in that range when you set the date, you may risk charging the movement. 

To set the time you have to pull the crown out to the second position when the second hand is at the 12 o’clock position. Then you turn the crown to advance the hands until the date changes to the next one. The time is already set for the am period. You then advance the hands to set the correct time. The date is set at the first click of the crown. 

How is the compass used? As stated in the manual, “The compass only works in the northern hemisphere, and may not work properly at lower latitudes (south of the Tropic of Cancer) depending on the season. You can only use it in places where the direction of the sun can be determined.”

What is there to do? While keeping the dial horizontal, point the hour hand in the direction of the sun. The south direction is indicated by the midpoint of the arc drawn between the 12 o’clock marker and the hour indicated by the hour hand.

Can magnetism affect this watch? Yes, like all mechanical watches. We recommend keeping it at least 5 cm away from any source of magnetism. You will notice this because your watch works quickly and will not correctly tell the time. 

Conclusion: Is it worth buying the Seiko Prospex Alpinist SPB121J1 automatic watch?

It’s a Seiko classic, and this new version has a better caliber than the old one. You can only be thrown back by the “cyclops” in the date window. For the rest, a few faults can be put on this automatic watch.

It has a really striking green dial and gold indexes/numbers. It has a basic compass, a very striking leather strap, and a Caliber with a very good power reserve of up to 70 hours. What more can you ask for in this price range?

If you like the design of the watch and its face, you may also like the:

In favor:

  • Classic and recognizable Seiko design
  • Sapphire crystal and leather strap
  • with compass
  • Large power reserve with up to 70 hours
  • 200-meter water resistance
  • Updated 6R35 caliber


  • You can love or dislike the magnifying glass to the fullest
  • You can see it is small on the wrist

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