Case #626 — Omega Seamaster 300 Professional (Black) Ref. 210.30.42.20.01.001

Case #626 — Omega Seamaster Diver 300M Co-Axial Master Chronometer 42 mm "Black Wave"

Ref. 210.30.42.20.01.001

Status: Available

Condition: Excellent Pre-Owned

Scope: Box, Papers, and Cards

Year: 2023

🔎 Case Notes

Some watches earn their reputation through scarcity. This one earned it through sheer competence. The Seamaster Diver 300M in full black is the reference that most people picture when they picture an Omega dive watch — and the 2018-generation redesign is the version that finally gave the design the movement and materials it had always deserved.

What separates this configuration from the field is the dial. It is not painted, printed or lacquered metal: it is polished black ceramic, laser-engraved with the signature wave pattern, with a date window at 6 o'clock. In daylight the waves disappear into a mirror-black surface; at an angle they catch and run across the dial like the real thing. Paired with the black ceramic bezel and its white enamel diving scale, the result is monochrome without being flat.

Inside is the Co-Axial Master Chronometer Calibre 8800, certified by METAS and resistant to magnetic fields up to 15,000 gauss, visible through the sapphire caseback. Power reserve runs to 55 hours.

A 2023 example in Excellent Pre-Owned condition, supplied complete as Box, Papers, and Cards. No specific condition flaws were recorded during inspection. The bracelet is currently sized for an approximately 7¾-inch wrist.

🕰️ The Evidence

• Reference: 210.30.42.20.01.001
• Model / Collection: Omega Seamaster Diver 300M Co-Axial Master Chronometer 42 mm
• Year: 2023
• Case: Stainless steel, brushed and polished
• Case Diameter: 42 mm
• Thickness: 13.56 mm
• Lug-to-Lug: 49.9 mm
• Lug Width: 20 mm
• Dial: Polished black ceramic with laser-engraved waves, date window at 6 o'clock, rhodium-plated raised indexes
• Hands: Rhodium-plated skeleton hands with Super-LumiNova
• Crystal: Domed scratch-resistant sapphire with anti-reflective treatment
• Bezel: Unidirectional rotating black ceramic bezel with white enamel diving scale
• Crown: Screw-down
• Caseback: Transparent sapphire exhibition back
• Movement: Omega Co-Axial Master Chronometer Calibre 8800
• Movement Type: Self-winding, automatic winding in both directions, free-sprung balance with silicon balance spring
• Certification: Certified Master Chronometer, approved by METAS; resistant to magnetic fields reaching 15,000 gauss
• Power Reserve: 55 hours
• Functions: Hours, minutes, seconds, date
• Water Resistance: 300 m / 1000 ft; helium escape valve
• Bracelet: Stainless steel, brushed and polished
• Clasp: Foldover clasp with comfort setting and diver extension
• Bracelet Fit: Approximately 7¾-inch wrist
• Condition: Excellent Pre-Owned
• Factory Warranty: Omega five-year factory warranty — see note below
• Included: Box, Papers, and Cards

🌟 Collector Provenance

The Diver 300M lineage begins in 1993, and for twenty-five years the model carried the same basic visual grammar: wave dial, skeleton hands, helium escape valve at 10 o'clock, scalloped bezel. It is one of the few modern dive watches whose silhouette is recognisable at conversational distance, and it achieved that without borrowing from anyone.

In 2018, for the model's 25th anniversary, Omega comprehensively revised the Diver 300M and revived the wave pattern on the dial. That revision is the dividing line collectors care about. The 2018 generation retained the wave dial and skeleton hands of the 1993 reboot while adding ceramic for the unidirectional dive-scale bezel, a case enlarged to 42 mm, and — most significantly — the in-house Master Chronometer certified Co-Axial Calibre 8800.

Within that generation, the full-black steel-on-steel version is the anchor reference. It is the most straightforwardly useful of the range: no two-tone, no gold accents, no colour that dates. Collectors who own several Seamasters tend to keep this one, because it is the configuration that works on a Tuesday morning as readily as it does on a boat.

The ceramic dial deserves a specific mention. Omega could have delivered the wave pattern far more cheaply in stamped metal — earlier generations did exactly that. Using zirconium-oxide ceramic and laser-engraving the waves into it was a materials decision that most buyers will never notice on a spec sheet and every buyer notices in person.

🌟 Technical Provenance

Master Chronometer is not marketing shorthand for "accurate". It is a METAS-approved certification layered on top of chronometer testing, with resistance to magnetic fields reaching 15,000 gauss, achieved through a free-sprung balance with a silicon balance spring rather than soft-iron shielding. The practical consequence is that the movement can be put behind a display caseback — which Omega does here — instead of hidden inside an anti-magnetic cage.

That matters more now than it did in 1993. Laptop closures, tablet covers, wireless chargers, magnetic phone mounts and cabinet catches are the routine hazards of a modern week, and they are the most common reason a mechanical watch suddenly starts running fast. The 8800 is engineered to be indifferent to all of them.

The rest of the specification is conventional dive-watch discipline executed properly: 300 m water resistance, a screw-down crown, a helium escape valve, a unidirectional ceramic bezel that cannot be accidentally rotated to overstate remaining air, and a domed anti-reflective sapphire crystal that keeps the dial legible rather than mirrored.

🧾 From the Case File

On the wrist, the numbers tell a kinder story than the 42 mm headline suggests. A 49.9 mm lug-to-lug and 13.6 mm height mean the case sits within the footprint of most medium wrists rather than overhanging them, and the lugs curve down hard. This is a watch that wears its diameter rather than announcing it.

The foldover clasp includes a comfort setting and a diver extension — meaningful in daily use, because wrists swell in heat and shrink in cold, and the comfort adjustment handles that without tools or a trip to a watchmaker. The bracelet is currently sized for an approximately 7¾-inch wrist; links can be added or removed by any competent watchmaker.

The 20 mm lug width is the most widely supported size in the aftermarket, so rubber, NATO and leather alternatives are easy to source should you want a second look.

The case for this particular example is completeness and currency. It is a 2023 watch, graded Excellent Pre-Owned, arriving as Box, Papers, and Cards — the configuration most collectors want and the one most difficult to reassemble after the fact. Current production Diver 300M references remain in the catalogue, which means parts, service and support are entirely routine rather than a future problem.

🗝️ BST Verdict

The reference most people mean when they say "Omega diver", in its most wearable configuration: black ceramic dial, black ceramic bezel, steel bracelet, nothing superfluous.

A 2023 example in Excellent Pre-Owned condition with Box, Papers, and Cards, running the METAS-certified Calibre 8800. Based on the 2023 date, this watch should remain within Omega's five-year factory warranty period — subject to the exact warranty-card activation date and Omega's warranty terms, which we recommend confirming directly.

Buy it to wear. It was designed for exactly that.

👉 Every case deserves a closer look.