OMEGA · Seamaster Diver 300M and Speedmaster Moonwatch Professional
OMEGA 210.30.42.20.01.001 vs OMEGA 310.30.42.50.01.001
10 published specifications differ between these two, and 6 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.
What differs
| Specification | OMEGA Seamaster Diver 300M 42mm, black dial210.30.42.20.01.001 | OMEGA Speedmaster Moonwatch Professional 42mm, Hesalite310.30.42.50.01.001 |
|---|---|---|
| Thickness | 13.56 mm | 13.54 mm |
| Lug to lug | 49.9 mm | 47.5 mm |
| Water resistance | 30 bar (300 metres / 1,000 feet) | 5 bar (50 metres / 165 feet) |
| Crystal | Domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides | Hesalite crystal with OMEGA logo in the centre |
| Clasp | Foldover clasp with comfort setting and diver extension | Foldover clasp with comfort setting |
| Calibre | Calibre OMEGA 8800 | Calibre OMEGA 3861 |
| Movement | Self-winding movement with Co-Axial escapement, automatic winding in both directions | Manual-winding chronograph movement with Co-Axial escapement |
| Power reserve | 55 hours | 50 hours |
| Frequency | 3.5 Hz | 3 Hz |
| Movement notes | Resistant to magnetic fields reaching 15,000 gauss. Free sprung-balance with silicon balance spring. Rhodium plated finish with Geneva waves in arabesque. Total product weight approximately 194 g. | Resistant to magnetic fields reaching 15,000 gauss. Free-sprung balance with silicon balance spring; rhodium-plated finish with bridges carrying straight Geneva waves. Total product weight approximately 134 g. |
What is identical
Worth knowing as much as the differences: these are the specifications you cannot use to tell the two apart.
- Case
- Steel, 42 mm
- Diameter
- 42 mm
- Lug width
- 20 mm
- Dial
- Black
- Bracelet
- Steel
- Certification
- Master Chronometer, approved by METAS
What the differences cost you
Each note below follows from the published figures in the tables above — what they mean for intake, for a listing, and for the handover. Nothing here estimates a price or a margin.
One of these is the harder fit
Lug to lug is 49.9 mm on the 210.30.42.20.01.001 against 47.5 mm on the 310.30.42.50.01.001 — a 2.4 mm difference across the wrist. Diameter is what buyers ask about; lug to lug is what decides whether a case sits flat or overhangs. Ask for a wrist measurement before shipping the 210.30.42.20.01.001, and put the figure in the listing rather than the diameter alone.
Do not describe these the same way
The 310.30.42.50.01.001 is rated to 50 metres and the 210.30.42.20.01.001 to 300. A rating is a factory figure for a new watch with fresh gaskets, not a promise about a used one — but the gap still matters in writing. Describe the 310.30.42.50.01.001 in words a buyer can act on, and do not let a template carry the 210.30.42.20.01.001's language onto it.
Two different ownership conversations
The 210.30.42.20.01.001 is self-winding and the 310.30.42.50.01.001 is hand-wound. That changes what a buyer needs telling at handover, and it changes intake: a hand-wound watch has no rotor to mask a tired mainspring, and a stopped quartz watch is usually a battery rather than a fault.
Different movements to verify and to service
The 210.30.42.20.01.001 runs the Calibre OMEGA 8800 and the 310.30.42.50.01.001 the Calibre OMEGA 3861. Two consequences at intake: the service history that is normal for one calibre is not evidence about the other, and the calibre is the check that catches a movement swapped into the wrong case. Confirm the movement matches the reference rather than assuming it from the dial.
What to check on each
210.30.42.20.01.001
- Confirm the calibre is the 8800 and not the 8900 used in the Aqua Terra. They are different movements with different reserves, and the 8800 has no time zone function to demonstrate.
- Check the crown screws down properly. At 300 metres this is a genuine dive rating and the crown is a primary seal, so any binding or reluctance to seat matters.
- Look at the anti-reflective coating on the inner crystal face as well as the outer. Interior hazing cannot be polished and means the crystal is due for replacement.
310.30.42.50.01.001
- Identify the crystal before anything else. Hesalite is a plastic: it scratches easily, polishes out with a cloth and compound, and carries a small OMEGA logo etched at its centre. A sapphire crystal on this case means you are looking at a different reference number.
- Do not treat scratches on a Hesalite crystal as damage in the way you would on sapphire. They are expected and largely removable, and pricing them as permanent faults misreads the material.
- Check the 3861 is what is fitted. The Moonwatch has used several calibres across its history, and the Master Chronometer 3861 is the current one — papers and caseback should agree.
Sources
- OMEGA official product page for reference 210.30.42.20.01.001 (Seamaster Diver 300M Co-Axial Master Chronometer 42 mm; steel) - Case: steel; 42 mm; Dial color: black; Crystal: domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides; Water resistance: 30 bar (300 metres / 1000 feet); Movement: Calibre OMEGA 8800; self-winding movement with Co-Axial escapement; certified Master Chronometer approved by METAS; resistant to magnetic fields reaching 15000 gauss; free sprung-balance with silicon balance spring; automatic winding in both directions; rhodium plated finish with Geneva waves in arabesque; Power reserve: 55 hours; Frequency: 3.5 Hz; listed with a 5-year warranty; Re-read 2026-09-23, the page additionally publishes: Between lugs: 20 mm; Lug-to-lug: 49.90 mm; Thickness: 13.56 mm; Case diameter: 42 mm; Total product weight (approx.): 194 g; Type of Clasp: Foldover clasp with comfort setting and diver extension; Bracelet material: Steel — retrieved 2026-09-23
- OMEGA official product page for reference 310.30.42.50.01.001 (Speedmaster Moonwatch Professional Co-Axial Master Chronometer Chronograph 42 mm; steel on steel) - Case: steel; 42 mm; Dial color: black; Crystal: hesalite crystal with OMEGA logo in the centre; Water resistance: 5 bar (50 metres / 165 feet); Movement: Calibre OMEGA 3861; manual-winding chronograph movement with Co-Axial escapement; certified Master Chronometer approved by METAS; resistant to magnetic fields reaching 15000 gauss; free-sprung balance with silicon balance spring; rhodium-plated finish with bridges carrying straight Geneva waves; Power reserve: 50 hours; Frequency: 3 Hz; the watch is listed with a 5-year warranty and as Swiss Made; Re-read 2026-09-23, the page additionally publishes: Between lugs: 20 mm; Lug-to-lug: 47.50 mm; Thickness: 13.54 mm; Case diameter: 42 mm; Total product weight (approx.): 134 g; Type of Clasp: Foldover clasp with comfort setting; Bracelet material: Steel — retrieved 2026-09-23
Not affiliated with OMEGA. Specifications are read from each manufacturer's own published documentation on the dates shown and may change; the manufacturer's current documentation governs.