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The watch in this title is almost certainly OMEGA’s Seamaster Diver 300M Co-Axial Chronometer GMT Chronograph, reference 212.30.44.52.03.001. OMEGA’s Japan product page lists it as a 44 mm stainless-steel model. A 2022 retailer review reports a case thickness of 17.8 mm and a lug-to-lug span of 52 mm. Whether it suits you depends mainly on your wrist width and on whether you need a GMT function alongside the chronograph.
The title does not name a reference, so this article treats the 44 mm GMT chronograph as its subject. It is not a guide to every Seamaster 300M chronograph.
Which watch the title refers to
Several OMEGA models share the Seamaster Diver 300M name, and they differ in size and function. The table below compares the reference this article covers with the older Seamaster 300M it is often confused with.
| Reference | Case diameter | Calibre | Complications listed |
|---|---|---|---|
| 212.30.44.52.03.001 (Diver 300M Co-Axial Chronometer GMT Chronograph) | 44 mm, stainless steel (OMEGA Japan product page) | Not stated on the product page reviewed | Chronograph and GMT (OMEGA Japan product page; the 2022 retailer review lists the same functions) |
| 2225.80.00 (earlier Seamaster 300M) | 41.5 mm (OMEGA Hong Kong product sheet) | 1164 (OMEGA Hong Kong product sheet) | Not stated on the product sheet reviewed |
OMEGA’s chronograph collection also includes other 44 mm Diver 300M chronographs. A shared model name does not mean a watch has a GMT function, so check the full reference before comparing or buying.
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Specifications at a glance
- Reference: 212.30.44.52.03.001, as listed on OMEGA’s Japan product page (checked 9 October 2026).
- Case: 44 mm, stainless steel.
- Case thickness: 17.8 mm. This figure comes from a 2022 retailer review and has not been checked against OMEGA’s own measurements.
- Lug-to-lug: 52 mm, from the same retailer review and subject to the same caveat.
- Functions: hours, minutes, small seconds, date, GMT and chronograph, per the retailer review’s feature list.
- Water resistance: the Diver 300M name is part of the model’s product name. The official product page used for identification does not state the rating in a form that can be quoted here, so confirm it in OMEGA’s full specifications before relying on it for diving.
Will the size fit your wrist?
Case diameter alone tells you little about wearing comfort. Lug-to-lug span, the distance from the tip of the top lug to the tip of the bottom lug, determines whether the watch sits within the edges of your wrist. The 52 mm figure is the one to check first.
How to check the lug-to-lug fit
- Wrap a flexible tape around your wrist to get its circumference, then measure the width across the back of the wrist where the watch would sit, using a flat ruler or a hard tape.
- Compare that width with 52 mm. If the lug tips would extend well past the edges of your wrist, the watch will overhang. Overhang is a general fit principle, not a figure from OMEGA or the retailer, so use your own judgement on what looks and feels right.
- Test the thickness separately. At 17.8 mm, the case is thick enough to catch under a shirt cuff or jacket sleeve, so consider how you dress as well as how the watch sits on your wrist.
What the chronograph and GMT functions add
Chronograph
The chronograph provides stopwatch timing on top of the time display. It is the function most people associate with this model family, and it is what distinguishes the reference from a plain time-only Diver. The retailer review lists the function but does not describe pusher layout or timing operation, so consult OMEGA’s instructions for the exact controls.
Rank #2
- Model 212.30.44.52.01.001
GMT
The GMT function adds a 24-hour hand so you can read a second time zone alongside your local time. This is the feature that separates the reference covered here from the non-GMT 44 mm chronographs in OMEGA’s range. Confirm the hand and bezel behaviour in OMEGA’s documentation before relying on it for travel.
Date and small seconds
The small seconds sub-dial and the date window are standard features in this model’s listed function set. Neither changes the wearing considerations above.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteRank #3
- Omega Seamaster Automatic Chronometer Black Dial Men's Watch 210.30.42.20.01.001
What this article does and does not test
This is a specification and fit guide. It is built from OMEGA’s product page, OMEGA’s Hong Kong product sheet for the older reference, and a 2022 retailer video review. It does not report firsthand wear, comfort, timing accuracy, lume performance or water testing. Those points need to be assessed on a physical watch or by a reviewer who has tested one.
Checklist before buying a new or pre-owned example
- Confirm the reference 212.30.44.52.03.001 on the listing, and check that the description matches the GMT chronograph rather than a time-only Diver 300M.
- Check the case diameter (44 mm) and, if you can, the lug-to-lug measurement against your own wrist.
- For a pre-owned watch, ask for the original box and papers, any service history, and clear photos of the case, bracelet or strap and dial.
- Compare current price and stock on OMEGA’s official site and on at least one other seller. Prices and availability change, and this article does not state them.
- Ask whether a seller’s condition description has been verified by an independent party, and treat undocumented condition claims with caution.
Who this watch suits
The reference named in the title is a large, thick GMT chronograph. It suits a reader who wants a 44 mm dive-style chronograph with a second time zone, and whose wrist is wide enough to carry 52 mm of lug-to-lug without overhang. It is a poor choice for smaller wrists, for anyone who wears watches under a close cuff, or for anyone who wants a slimmer GMT. For those readers, check the lug-to-lug and thickness figures against the alternatives before deciding.
Quick Recap
Best Value
- Rubber
- Rotating bezel, gmt
- Automatic-self-wind movement
- Case diameter: 40mm
- Water resistant to 330 feet
Rank #4
- Model 210.90.42.20.01.001
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
