The Sea-Gull ST2130 is an automatic mechanical movement with a 28,800-vibration-per-hour frequency, 28 jewels and a stop-seconds function. It is worth considering when you want a 4Hz mechanical watch, but the calibre name alone does not establish accuracy, water resistance or the quality of the complete watch.
This guide separates Sea-Gull's published movement specification from the features of current watches sold by Watchdives. It also explains our WD0019 V-Grade wording. It is a specification-led buying guide, not a long-term reliability test.
ST2130 specifications at a glance
Sea-Gull's TY2130/ST2130 movement listing is the source for the following reference specifications.
| Specification | Published reference |
|---|---|
| Type | Automatic mechanical |
| Frequency | 28,800 vibrations per hour, equivalent to 4Hz |
| Jewels | 28 |
| Power reserve | 40 hours in Sea-Gull's referenced listing |
| Movement thickness | Approximately 4.8mm |
| Maximum movement diameter | Approximately 26.00mm |
| Listed functions | Central hour, minute and seconds hands; date at 3 o'clock; stop-seconds |
These are movement specifications, not case dimensions. A watch using this calibre may have a different dial layout, including no visible date window. Use the exact watch listing and instructions for its delivered configuration.
What does 4Hz mean on the wrist?
At 28,800 vibrations per hour, there are eight beats per second: 28,800 divided by 3,600. The balance completes four full oscillations per second, hence 4Hz. This should not be confused with a seconds hand making four complete rotations per second.
The practical attraction is the finer-stepped appearance of the seconds hand. Frequency is not a daily accuracy guarantee: an advertised beat rate and a measured gain or loss in seconds per day describe different things.
ST2130 vs NH35: what actually changes?
TMI lists the NH35 at 21,600 vibrations per hour, or 3Hz, with 24 jewels and stop-seconds in its official NH-series specifications. That means six beats per second rather than eight. Choose the ST2130 when the 4Hz character is a feature you specifically value; do not treat the frequency or jewel count as a complete quality ranking.
When comparing finished watches, check case proportions, bracelet comfort, crystal, dial legibility and service arrangements alongside the movement. Paying for a different calibre is only worthwhile if the whole watch matches your priorities.
Accuracy and V-Grade: what the wording does and does not promise
The WD0019 Premier listing describes V-Grade as the highest level in our Sea-Gull movement grading system, with stricter selection and higher cost than AAA or lower-grade versions. This describes the selection used for that Watchdives product; it should not be transferred to every watch carrying an ST2130.
Neither that label nor the movement's frequency establishes a specific daily-rate tolerance by itself. This guide does not turn V-Grade into a universal industry certification or invent a seconds-per-day promise. Ask for the stated tolerance and test conditions for the exact watch when accuracy is a deciding factor.
For the separate changes to hand lume and quality-control checks on WD0019, read our WD0019 production update. Movement selection and those finished-watch changes are different subjects.
Two current ST2130 watches with different priorities
Both listings below were checked on September 28, 2026. They illustrate why sharing a movement does not make two watches interchangeable.
| Watch | Listed dimensions | What to compare |
|---|---|---|
| Watchdives Premier WD0019 | 39mm case / 40mm bezel; 47.5mm lug-to-lug; 12mm thick including crystal | Sapphire exhibition back, OTF adjustable clasp and stated 200m water resistance; the shorter, thinner steel option here |
| San Martin SN0036-GC | 41mm case / 40mm bezel; 48.5mm lug-to-lug; 13.4mm listed thickness | Steel case, OTF adjustable clasp, helium escape valve and stated 600m water resistance; a larger case despite the same bezel diameter |
Water-resistance figures belong to the complete watch. They do not come from the ST2130 and do not by themselves establish dive certification. Check the manufacturer's activity guidance and the current condition of the watch before water use.
Start with WD0019 if an exhibition back and the smaller case are priorities. Compare SN0036-GC if you prefer its larger proportions and stated case specification. Neither is automatically the better watch because of its depth number. Current price, stock and available options remain on the linked product pages.
Power reserve, winding and ownership
The WD0019 listing specifies approximately 39-40 hours of reserve and supports hand-winding and hacking seconds. A reserve of that length is not a promise that a watch left off the wrist all weekend will still be running on Monday. Restart and set it according to the instructions for the exact model.
Do not infer crown positions or a universal safe date-setting window from the calibre name alone. Ask for the correct operating instructions when the watch has a different dial configuration or an unfamiliar crown.
For an accuracy concern, keep a simple record using the same reference clock over several days, noting when the watch was worn or left unworn. This gives the service team more useful information than a single reading. Do not open or regulate the movement as a first troubleshooting step; contact the seller for assessment. Our Watchdives warranty and repair guide explains how to request help with an order.
Quick answers
Is ST2130 a quartz movement?
No. It is mechanical. For the broader ownership choice rather than this calibre, see our quartz vs automatic comparison.
Is every ST2130 watch V-Grade?
No such conclusion follows from the calibre name. The V-Grade description here applies to the specific Watchdives listing that states it.
Can I assume an ST2130 will fit another movement's case?
No. A diameter and thickness comparison is not a complete compatibility check. A watchmaker must confirm the required dial, hands, stem, calendar alignment and case fit before any replacement.
Does this guide prove long-term reliability?
No. We have not presented a controlled failure-rate study or long-term comparative test. Published specifications answer what the movement offers; actual condition, product-specific checks and after-sales support need separate evidence.
Sources and product listings checked September 28, 2026. Manufacturer references describe the cited movement configurations; product pages describe the finished watches. Prices and stock are intentionally not fixed in this guide.
