Monaco square water-resistant case

Probable

The first square water-resistant chronograph case, made by Erwin Piquerez SA to a patented construction. Sealing a square case is materially harder than sealing a round one, which is why the Monaco's case is a manufacturing achievement rather than a styling exercise — and why the case's construction, not its shape, is what an examiner should read.

Part reference

Brand: TAG Heuer
Maker: Erwin Piquerez SA (period supplier)
Material: Stainless steel
Introduced: 1969
Identifying marks: Case-maker marks inside the caseback. Crisp, even edges to the square profile with consistent brushing across the flat surfaces; the crystal seats square with no gap at the corners, which is where a reproduction case most often fails.

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.

Left-hand crown
FactoryProbable
Whole production
Correct on Caliber 11-family examples, and a consequence of the movement's module rather than a design choice. A left crown on a Monaco is therefore a caliber statement.
Right-hand crown
FactoryProbable
Whole production
Correct on later references built around conventional calibers, including the modern Heuer 02 Monacos. On a watch presented as a Caliber 11-era Monaco it warrants establishing what is actually inside.

Documented on these references

TAG Heuer 1133BFactory
Whole production
Left-hand crown, following from the Caliber 11's module. The case's sealing construction is what makes it significant, not its shape.
TAG Heuer CAW211P.FC6356Factory
Whole production

Provenance of this record

Sources & Evidence

Secondary sourceCollector research

Heuer collector research on reference numbering, dial generations and executions

Collector communities and specialist dealers

Accessed: 2026-08-18

Cited for

This referenceProbable

Primary sourceManufacturer archive

TAG Heuer heritage archive and museum holdings

TAG Heuer SA, Le Locle

Accessed: 2026-08-18