Swiss St. Bernard Poincon, Au750 Scales & Place Vendome Eagle Head Hallmarks: Complete Metallurgical Guide

What Does the Swiss St. Bernard Poincon Mean on an 18K Gold Watch?

The Swiss St. Bernard dog head hallmark (Poincon d'origine bernard) is the sovereign official stamp of the Central Office for Precious Metals Control in Bern, certifying that a horological case contains at least 750 parts per thousand (75.0%) pure elemental gold or 950 parts per thousand (95.0%) pure platinum. Introduced on August 1, 1995, to replace the historical Helvetia female profile, the St. Bernard mark applies uniformly to domestic and exported Swiss precious-metal watch cases. Under a 20x triplet loupe, a genuine cold-struck or precision laser-ablated St. Bernard hallmark exhibits a distinct micro-collar outline and a tiny letter "G" or assay office cipher nestled beneath the dog's chin.

At 18K Solid Gold Salon Place Vendome, every solid 18K yellow, Everose, and white gold timepiece in our archive undergoes microscopic hallmark verification alongside non-destructive spectroscopy. Whereas electroplated or PVD-coated stainless steel replicas rely on shallow acid-etched markings that blur under 10x magnification, solid Au750 bullion cases display sharp vertical walls inside the stamp cavity because the 18-karat alloy flows cleanly under hydraulic coining pressure.

How Are Au750 Balance Scale and Eagle Head Marks Verified by XRF?

A physical hallmark on a watch lug is only authoritative when corroborated by non-destructive X-Ray Fluorescence (XRF) elemental spectroscopy and gravimetric mass measurement. During our Place Vendome pre-shipment protocol, a Fischer Fischerscope XRF analyzer directs a collimated primary X-ray beam onto the hallmarked lug, exciting the inner atomic shells of the alloy. A genuine solid 18K gold case emits characteristic L-alpha (9.71 keV) and L-beta (11.44 keV) fluorescence photons corresponding to 75.00%–75.40% gold (Au), balanced by 12%–16% silver (Ag), 8%–12% copper (Cu), and 1.5%–2.2% platinum or palladium in Everose and white gold formulations.

Crucially, the XRF spectrum must show 0.00% iron (Fe), 0.00% nickel (Ni), and 0.00% tungsten (W) across both the outer lug bevels and the inner spring-bar holes. When paired with a calibrated Mettler-Toledo 0.01g analytical balance readout—confirming 216.5g on a full-bracelet yellow gold chronograph or 186.8g on a rose gold integrated sports watch—the collector receives irrefutable mathematical proof of solid precious-metal construction.

Where Are Hallmarks Located on Rolex, Patek Philippe, and Audemars Piguet Cases?

Each Geneva and Le Brassus manufacture follows a strict architectural convention for hallmark placement to preserve the mirror-polished and satin-brushed geometry of the visible case flanks. On solid 18K gold and Pt950 Rolex Oyster cases (including the Cosmograph Daytona, Day-Date 40, Sky-Dweller, and Submariner), four recessed stamps are struck into the flat underside of the four lugs: the 750 balance scales, the Swiss St. Bernard dog head, the Rolex coronet, and the maker's responsibility mark, complemented by deep stamps on the inner Oysterlock or Crownclasp folding blades.

On Patek Philippe Nautilus and Aquanaut references with sapphire exhibition casebacks, the 750 scale mark, St. Bernard poincon, and Calatrava cross are positioned along the satin-brushed underside of the octagonal case ears and on the inner wing of the fold-over deployant clasp. On Audemars Piguet Royal Oak models, the hallmarks flank the eight hexagonal caseback screws at the 12 and 6 o'clock segments, framing the hand-finished 22-karat or 18-karat gold oscillating weight visible through the sapphire crystal.