OMEGA Ultra Deep 215.30.46.21.03.002: specs and what to check

Every number is an outlier

Set this reference against everything else documented on this site and it occupies the far end of four separate scales at once.

• Water resistance — 600 bar. Ten times the next deepest OMEGA here, and ahead even of the Rolex Deepsea's 3,900 metres.
• Thickness — 18.12 mm. The next tallest anywhere here is 15.7 mm.
• Weight — 254 g. The next heaviest is 194 g.
• Lug to lug — 51.90 mm. The next longest is 50.9 mm.

None of that is a criticism; it is what a six-thousand-metre case costs. But it does mean the usual dealer shorthand fails completely. "Forty-five and a half millimetres" tells a buyer almost nothing about what is about to arrive.

All four belong in the listing, spelled out, long before the parcel is packed. Sending a quarter-kilo watch back costs real money in postage alone, and four figures you already hold prevent it.

O-MEGASTEEL is a name, not a description

OMEGA specifies both the case and the bracelet as O-MEGASTEEL — a proprietary alloy it names rather than a generic stainless.

Write it that way. "Stainless steel" is a reasonable-sounding paraphrase and it throws away the specific thing the manufacturer said, which on a reference like this is part of what a buyer is paying attention to.

It also matters for parts. A bracelet or clasp component sourced from an ordinary steel OMEGA is not the same material, and on a matched set the difference in colour and finish is visible in the hand.

A crystal that sticks out on purpose

The crystal is specified as domed, protuberant and scratch-resistant sapphire, with anti-reflective treatment on both sides.

Protuberant is doing real work in that sentence. The glass stands deliberately proud of the case — that geometry is part of how the crystal resists pressure — and it means the crystal, not the bezel, is the highest point on the watch.

Inspect it accordingly. Tip the watch until light rakes along the raised edge and travel the full circumference looking for chips. Sapphire does not wear gradually; it looks perfect and then flakes, and a chip on a curved raised edge is nearly invisible from straight above.

Then look through it for interior haze, and across it for damage to the outer coating. Both faces are treated here, so there are two coatings to assess.

The clasp is carrying a quarter of a kilo

Foldover clasp with comfort setting and diver extension, in O-MEGASTEEL, on a watch that weighs 254 grams.

Open the extension completely and confirm the hinge is sound and that it folds away flat. Run the comfort adjustment through every detent and check it holds under a pull rather than sliding. Close everything and hang the watch from the clasp with a firm tug.

This is the single most consequential mechanical check on the reference. Nothing else on the watch fails in a way that puts it on the floor.

The movement is the ordinary part

Calibre 8912, self winding, 60 hours, Master Chronometer certified — the same movement OMEGA fits to the Planet Ocean 600M and the 41 mm Seamaster.

Which is the point worth making to a buyer: what you are paying for here is the case, not the calibre. The engineering that separates this watch from a 300-metre Seamaster is entirely on the outside.