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Crown

Helium escape valve (10 o'clock)

High confidence

A one-way valve in the case flank at 10 o'clock, fitted to the Seamaster Diver 300M and the Planet Ocean. It exists to vent helium that has permeated the case during saturation diving, so that the crystal is not pushed off during decompression — a problem confined to divers living in a helium-rich habitat and irrelevant to every other use. Its position at 10 o'clock, opposite the crown, is a defining feature of the case: a Diver 300M case with no valve boss is either a different model or a different case.

Part reference

Brand
Omega
Material
Stainless steel with gaskets
Introduced
1993
Identifying marks
Machined boss on the left flank with a knurled or screw-down head depending on generation, aligned and finished to the same standard as the case. Crooked, proud or roughly finished valves are a common counterfeit tell.

Documented variations

Classification

FactoryDocumented as shipped from the factory for this reference and period.PeriodNot original to this watch, but correct for its production period.ServiceFitted by the manufacturer's own service network. Not a defect.AftermarketThird-party part. Affects originality, not authenticity.ModifiedGenuine parts in a configuration the factory did not sell. Affects originality and value, not authenticity.CounterfeitDeceptive reproduction intended to pass as genuine.UnknownEvidence on file does not settle the question.

  • Manual screw-down valve

    FactoryProbable

    Whole production

    Requires unscrewing before decompression. Correct on the earlier references.

  • Automatic (conical) valve

    FactoryProbable

    Whole production

    Later automatic execution that vents without operation. A watch whose valve cannot be unscrewed is not necessarily faulty; it may simply be the automatic type.

Documented on these references

Provenance of this record

Sources & Evidence

Primary sourceManufacturer documentation

OMEGA instruction manuals and technical guides

OMEGA SA

Accessed
2026-08-18

Cited for

This referenceHigh confidence
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