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Dial&Lug
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SSK001 vs SSK023

Seiko SSK001 vs SSK023

Same 4R34 GMT caliber, same 100m, same $176 overhaul. One is a 42.5mm dive-styled case; the other a 39.4mm field case. The decision is your wrist.

By Sawyer V. · Published

The short answer

Buy the SSK023 if your wrist is under about 17cm or you want a field watch; buy the SSK001 if you want the dive-watch look. Inside they are the same: a 4R34 GMT, 100m, Hardlex, three years of warranty and Seiko's published $176 4R overhaul. The SSK023 is 39.4mm on a 20mm strap; the SSK001 42.5mm on 22mm.

Seiko's two affordable GMTs are the cleanest possible comparison: the same movement, the same rating, the same service price and the same thickness, in two different cases. Nothing on this page affects how long either watch lasts. What it affects is whether it suits your wrist and your wardrobe.

Side by side

From Seiko's product pages and published US service list.
SSK023SSK001
Case styleFieldDive-styled
Diameter39.4mm42.5mm
Lug-to-lug47.9mm46mm
Thickness13.6mm13.6mm
Lug width20mm22mm
Movement4R34 GMT4R34 GMT
Water resistance100m100m
CrystalHardlexHardlex
Published overhaul$176$176
From Seiko's product pages and published US service list.

On prices: we publish no figure we have not verified today, so every buy button reads "Check price on Amazon". Service prices on this page are the manufacturers' own published figures.

How we picked

We have not worn these watches. What follows is what we checked instead, on documents you can open yourself — the same criteria, in the same order, on every roundup on this site. The full method is on the methodology page.

  1. 01Case

    39.4mm field case against 42.5mm dive-styled case.

  2. 02Lug-to-lug

    47.9mm on the SSK023; 46mm on the SSK001, which is shorter than its diameter suggests.

  3. 03Strap

    20mm on the SSK023, 22mm on the SSK001. Both even, both commodity sizes.

  4. 04What they share

    4R34 GMT, 100m, Hardlex, 13.6mm thick, three years of warranty, $176 overhaul.

Disclosure · Some links below are Amazon affiliate links. If you buy through one we earn a commission at no extra cost to you. It does not decide what goes on this page or in what order — here is exactly how that works.

Quick picks

Ranked on the Keep Score below — six published specifications, weighted identically on every page. The last row is the one we would not buy.

#WatchBest forKeep ScorePrice
1

Seiko 5 Sports GMT SSK023

39.4mm field case, 4R34 GMT, 20mm strap.

Most wrists, and a quieter look8.0/10
Check price
2

Seiko 5 Sports GMT SSK001

42.5mm dive-styled case, 4R34 GMT, 22mm strap.

The dive-watch look8.0/10
Check price
—

Q Timex GMT 38mm TW2V38000

38mm and charming — acrylic, 50m and a one-year warranty.

Skip this one

Not the cheaper alternative to either5.6/10
Check price

Keep Score is arithmetic, not opinion — six published specifications, weighted the same way on every page. The formula is on our methodology page, so you can re-run it yourself.

01

Seiko 5 Sports GMT SSK023

Best for: Most wrists, and a quieter look

8.0/10

Keep Score

Crystal
1.3/2.5
Serviceability
2.5/2.5
Water resistance
1.1/1.5
Warranty
1.05/1.5
Strap standard
1/1
Cost-to-keep transparency
1/1
Check price on Amazon

#ad Affiliate link · We publish no price we have not verified today

At 39.4mm the SSK023 is the size most GMTs should be and very few are, and the field dial works with a shirt as readily as a T-shirt.

Its lug-to-lug is 47.9mm — slightly longer than the SSK001's, because the field case has conventional lugs.

Identical movement and identical service cost to the SSK001 in a case 3mm narrower. If the 42.5mm SSK001 is too much watch, this is the same purchase in a size more wrists can carry.

Manufacturer specifications for the Seiko 5 Sports GMT SSK023
MovementSeiko 4R34, automatic with manual winding, 24 jewels, 24-hour hand
Power reserve41 hours
Case39.4mm stainless steel
Lug-to-lug47.9mm
Thickness13.6mm
Lug width20mm
Crystalhardlex
Water resistance100m
Warranty3 years

Specifications read from Seiko Watch Corporation product page, SSK023.

02

Seiko 5 Sports GMT SSK001

Best for: The dive-watch look

8.0/10

Keep Score

Crystal
1.3/2.5
Serviceability
2.5/2.5
Water resistance
1.1/1.5
Warranty
1.05/1.5
Strap standard
1/1
Cost-to-keep transparency
1/1
Check price on Amazon

#ad Affiliate link · We publish no price we have not verified today

The original SSK: a 42.5mm dive-styled case with a 24-hour bezel, whose 46mm lug-to-lug wears shorter than the diameter suggests.

It is not a dive watch — 100m, no diver's marking — so buy it for the look.

The 4R34 is a caller GMT — the 24-hour hand is the one you set, not the local hand — but it is a real mechanical second time zone on a movement whose service price Seiko publishes.

Manufacturer specifications for the Seiko 5 Sports GMT SSK001
MovementSeiko 4R34, automatic with manual winding, 24 jewels, 24-hour hand
Power reserve41 hours
Case42.5mm stainless steel
Lug-to-lug46mm
Thickness13.6mm
Lug width22mm
Crystalhardlex
Water resistance100m
Warranty3 years

Specifications read from Seiko Watch Corporation product page, SSK001.

Skip this one

Q Timex GMT 38mm TW2V38000

Best for: Not the cheaper alternative to either

5.6/10

Keep Score

Crystal
1.8/2.5
Serviceability
1.6/2.5
Water resistance
0.6/1.5
Warranty
0.35/1.5
Strap standard
1/1
Cost-to-keep transparency
0.2/1
Check price on Amazon

#ad Affiliate link · We publish no price we have not verified today

The Q Timex GMT is the other affordable GMT these two are cross-shopped with, and at 38mm it is smaller than either.

It is rated 50m against the Seikos' 100m, runs a quartz movement, and carries Timex's one-year warranty excluding the crystal, strap, case and battery. The Seikos cost more and are the better watches to keep.

If size is why you looked at it, the SSK023 is 39.4mm.

A quartz GMT at 38mm, with an acrylic crystal you can polish and a battery any shop can change. It is not built like the mechanical GMTs on this site, but nothing about it is expensive to keep running.

Manufacturer specifications for the Q Timex GMT 38mm TW2V38000
MovementQuartz analog, SR920SW battery
Power reserveNot applicable
Case38mm stainless steel
Lug-to-lugNot published
Thickness12.5mm
Lug width18mm
Crystalacrylic
Water resistance50m
Warranty1 year

Timex's one-year warranty explicitly excludes the crystal, strap, case and battery.

Specifications read from Timex product page, TW2V38000.

How to choose, in one test

Measure your wrist. Under about 17cm, the SSK023 will sit better; over it, either works and the choice is style. Both GMTs set the 24-hour hand independently, which suits tracking home time — the GMT worth-it page covers when the complication earns its place.

Questions people actually ask

What is the difference between the Seiko SSK001 and SSK023?

The case. Both run the 4R34 GMT with 100m, Hardlex and a $176 published overhaul. The SSK023 is a 39.4mm field case on a 20mm strap; the SSK001 is a 42.5mm dive-styled case on a 22mm strap.

Which is smaller, the SSK001 or SSK023?

The SSK023 is narrower at 39.4mm against 42.5mm. Its lug-to-lug is slightly longer, 47.9mm against 46mm, because the field case has conventional lugs.

Is the Seiko SSK a true GMT?

It has an independently set 24-hour hand, which makes it what enthusiasts call a caller GMT — ideal for tracking a second zone, less convenient for resetting local time when you land.

How much does it cost to service a Seiko SSK?

Seiko publishes $176 for a 4R overhaul, which covers the 4R34 in both models.

Sources

Every specification and figure on this page came from one of these documents. Where a manufacturer does not publish something, the page says so rather than filling the gap.

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