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Seiko 5 Sports GMT SSK001
The watch that made mechanical GMT affordable, and the one limitation most reviews skip.
By Stephen V. · Updated Jul 24, 2026
The SSK001 is a 42.5 mm Seiko 5 Sports with a 46 mm lug-to-lug, 13.6 mm thickness and 22 mm lugs, running the 4R34 — a genuine mechanical caller GMT. It is rated 100 m with a Hardlex crystal and a rotating 24-hour bezel. The caller limitation is the thing to understand before buying.
What a caller GMT does
The 4R34’s independently adjustable hand is the 24-hour hand. The local hour hand is geared to the minute hand and cannot be jumped on its own.
That makes it a caller GMT: designed for someone who stays in one place and wants to see another time zone at a glance. Set local time normally, set the 24-hour hand to your reference zone, and you are done.
A traveler GMT works the other way — the local hour hand jumps in one-hour steps while the 24-hour hand keeps home time, which is what you want when you land somewhere and need to change local time without disturbing anything else. Seiko builds those in the 6R54 Prospex references, at several times this price.
| Your situation | The right movement |
|---|---|
| Colleagues or family in another zone | Caller (this watch) |
| You fly and change local time often | Traveler (not this watch) |
| You want a third zone via the bezel | Caller with rotating bezel (this watch) |
Getting a third time zone
The SSK001’s bezel is a rotating 24-hour scale, and that gives you a third zone: set local time on the hands, the 24-hour hand to zone two, then rotate the bezel so its offset against the 24-hour hand equals zone three.
The bezel-less SSK025 tracks two zones only, which is the practical difference between it and the SSK001 family — worth more than the dial color.
Sizing and case
It shares the 5KX case with the SRPD65, at 42.5 mm and 46 mm lug-to-lug, but is 13.6 mm thick rather than 13.4 mm because of the GMT works. That is a tall watch and it wears like one.
Like the rest of the 5 Sports line it is 100 m with a push-pull crown and no ISO 6425 marking. Swimming is fine; this is not a diver.
Setting it in the right order
Set the 24-hour hand first, then local time. Doing it the other way means re-checking the 24-hour hand, because on a caller movement the two are geared together and moving the hour hand moves the 24-hour hand with it.
The watches on this page
Specifications are transcribed from Seiko’s published documentation. Prices come from Amazon and carry the date they were verified. We have not handled these watches — here is what we did instead.
$495.0020% off
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports GMT SSK001
Seiko 5 Sports GMT SSK001
SSK001K1Best for: A second time zone on a mechanical movement, cheaply
The watch that made mechanical GMT affordable. A caller GMT in the 5KX case for roughly a third of what the complication used to cost.
- Spec completeness for the price
- 9.2
- Movement relative to bracket
- 9.4
- Case proportions
- 8.5
- Strap flexibility
- 9.5
- Availability
- 8.7
What it gets right
- Genuine mechanical GMT at a price nothing else matches
- Same 22 mm lugs and case footprint as the rest of the 5KX family
- Rotating 24-hour bezel adds a third zone
What it gets wrong
- Caller GMT, not a traveler GMT — the local hour hand does not jump
- Hardlex
- 13.6 mm thick
Skip this one if: you actually fly. A caller GMT is designed for tracking home from your desk; changing your local time zone on it means resetting the whole watch. Frequent travelers want a traveler (flyer) GMT, which Seiko sells only much higher up.
| Case diameter | 42.5 mm |
|---|---|
| Lug-to-lug | 46.0 mm |
| Thickness | 13.6 mm |
| Lug width | 22 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 100 m |
| Bezel | 24-hour bidirectional |
| Caliber | Seiko 4R34 |
| Type | Automatic GMT, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| GMT type | Caller (office) GMT — the 24-hour hand is independent |
$396.0010% off
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports GMT SSK005
Seiko 5 Sports GMT SSK005
SSK005K1Best for: The 4R34 GMT at the lowest price in the range
The orange-dial GMT. Identical mechanically to the SSK001, and usually the cheapest of the family on any given day.
- Spec completeness for the price
- 9.1
- Movement relative to bracket
- 9.4
- Case proportions
- 8.5
- Strap flexibility
- 9.5
- Availability
- 8.5
What it gets right
- Mechanical GMT
- Highest-contrast dial in the SSK line
- 22 mm lugs
What it gets wrong
- Caller GMT
- Hardlex
- Orange is a strong commitment
Skip this one if: you want one watch that goes everywhere. An orange dial is a decision you make every morning.
| Case diameter | 42.5 mm |
|---|---|
| Lug-to-lug | 46.0 mm |
| Thickness | 13.6 mm |
| Lug width | 22 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 100 m |
| Caliber | Seiko 4R34 |
| Type | Automatic GMT, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| GMT type | Caller (office) GMT — the 24-hour hand is independent |
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports Field GMT SSK025
Seiko 5 Sports Field GMT SSK025
SSK025K1Best for: A mechanical GMT that does not look like a dive watch
The 4R34 GMT in a field-style case instead of the diver-style one. If the SSK001's bezel is too much, this is the alternative.
- Spec completeness for the price
- 8.7
- Movement relative to bracket
- 9.4
- Case proportions
- 8.4
- Strap flexibility
- 9.2
- Availability
- 8.3
What it gets right
- Smaller 39.4 mm case
- Mechanical GMT
- 20 mm lugs
What it gets wrong
- Still 13.6 mm thick, so it wears taller than the diameter suggests
- No rotating bezel, so no third time zone
- Hardlex
Skip this one if: you wanted the bezel. Without a rotating 24-hour scale you get two zones, not three.
| Case diameter | 39.4 mm |
|---|---|
| Lug-to-lug | Not published by Seiko for this reference |
| Thickness | 13.6 mm |
| Lug width | 20 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 100 m |
| Caliber | Seiko 4R34 |
| Type | Automatic GMT, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| GMT type | Caller (office) GMT — the 24-hour hand is independent |
Questions
Is the Seiko SSK001 a true GMT?
Yes — a genuine mechanical 24-hour complication driven by the 4R34, not a quartz module or a decorative bezel. It is a caller GMT, so the 24-hour hand is the independently adjustable one.
Can the SSK001 track three time zones?
Yes. Local time on the hands, zone two on the 24-hour hand, and zone three by rotating the 24-hour bezel to the correct offset. The bezel-less SSK025 manages two.
What size is the Seiko SSK001?
42.5 mm diameter, 46 mm lug-to-lug, 13.6 mm thick, 22 mm lugs — the 5KX case, slightly taller than the standard SRPD because of the GMT mechanism.
Is the SSK001 water resistant enough to swim?
Yes, at 100 m. It has a push-pull crown and no ISO 6425 marking, so it is not a dive watch.
Why can't I change local time on a caller GMT?
The local hour hand is geared to the minute hand on the 4R34, so changing local time means pulling the crown and resetting the whole watch, including the seconds. That is the trade for the price.
Sources
- Seiko 5 Sports collection — official specifications
- Seiko Watch Corporation — US catalog and specifications
- Seiko Instruments — movement division (NH-series manufacturer)
- Seiko instruction manuals and caliber documentation
Specifications are transcribed from manufacturer documentation and published standards. Where a manufacturer does not publish a figure, this page says so rather than estimating one.