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Omega Seamaster Diver 300M 42mm, Green

Reference 210.30.42.20.10.001. A sheet to take with you: the numbers to check the watch against, what to look at, and what to ask. It does not authenticate anything and it does not tell you whether to buy.

Check the numbers

Measure or ask. A watch that does not match these is not necessarily wrong, but it is a question worth the answer.

Anything above marked not recorded is a gap in this catalog, not a property of the watch. Do not read a blank as a zero.

Before anything else

Mechanically and structurally this is the black 210.30.42.20.01.001 in a different colour, so the tells for any current Seamaster Diver 300M apply unchanged. What is specific to this reference is that both the dial and the bezel insert are ceramic, which behaves differently from paint and from aluminium when it is damaged or replaced.

What to look at

1. dial Laser-engraved waves in ceramic
   Correct Waves are cut into a polished ceramic surface and catch light at a different angle from the flat areas around them
   Red flag A printed or transferred wave pattern sitting on top of the dial surface, or waves whose depth is uniform under raking light
2. case Bezel insert colour through a chip
   Correct Ceramic is coloured through its whole thickness, so any chip shows the same green underneath
   Red flag A different colour or a pale substrate visible at a chipped edge, which indicates a coated insert rather than ceramic
3. movement Caliber 8800 and Master Chronometer certification
   Correct METAS-certified 8800 with a 55-hour reserve; the certificate card carries a number that matches the watch
   Red flag A missing certificate on a watch presented as full-set, or a reserve well short of 55 hours from full wind
4. crown Screw-down crown and helium escape valve
   Correct Crown threads down cleanly, and the helium valve at 10 is present and operates; the 300m rating depends on both
   Red flag A crown that will not seat, or a valve that turns without resistance

Known issues on this reference

• The dial itself is polished green ceramic with the waves laser-engraved into it, not printed on a brass base. A dial that shows the flat, slightly grainy look of paint under a loupe is not this reference’s dial.
• Green is the premium colourway in this family, which makes a repainted or swapped bezel insert on a cheaper reference the obvious thing to check for.
• Ceramic is hard but brittle: it resists scratching far better than aluminium and chips rather than scuffs when it takes a real knock. A green insert with soft scratches and no chips is worth a second look.

Parts that are commonly replaced

• Bezel inserts are replaced after damage. On a green reference this is also the swap that changes what the watch is worth, so ask when and by whom.
• Bracelet clasps and the diver extension are ordinary service items; confirm Omega markings.

Ask the seller, whatever the watch

• When was it last serviced, by whom, and is there paperwork?
• Has the case ever been polished?
• Which parts are not original to it?
• Do you have the box, papers and the original bracelet or strap?
• Why are you selling it?
• Can I see it in daylight, and can I take a photo of the caseback?

What this sheet is standing on

The specifications above are sourced to omegawatches.com, monochrome-watches.com. What else the catalog does not know.

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