Short answer
Fake IWC gold watches come in two forms: base metal cases with a gold coating, and gold cases that carry counterfeit IWC markings. A real IWC gold case is solid 18k gold, stamped 750. It weighs about twice what a steel case of the same size weighs, shows a Swiss hallmark next to the fineness stamp, and shows no gray or white base metal at the lug edges, crown, or caseback threads.
Marks to look for
- Fineness stamp: 750 or 18K, struck on the caseback or the inner caseback.
- Swiss hallmark: a St. Bernard dog head for gold, placed beside the fineness mark. Swiss assay offices use the dog head for gold, the goat head for platinum, and the swan for silver.
- Case material in the catalog entry for the reference number. IWC publishes the case material for each reference.
- Engraving quality: stamps on fakes sit shallow, sit uneven, or sit on a curve where a die would not reach.
Four checks you can run
- Density and weight. Fine gold is 19.32 g/cm3. 18k yellow gold runs about 15.2 to 15.9 g/cm3, rose gold about 15.0 to 15.5, white gold about 14.7 to 16.0. Steel is 7.9 g/cm3, brass about 8.5. A 40 mm solid gold case weighs about twice a steel one. Tungsten is 19.25 g/cm3 and copies gold weight, so a heavy case is not proof of gold.
- Magnet. 18k gold is not magnetic. Steel base metal is. A magnet pull means the case holds steel, not gold.
- Wear points. Gold plating runs from 0.5 microns to a few microns on common fake cases, up to about 20 microns on plated jewelry. Wear at the lugs, crown, and caseback threads exposes the alloy under the plate. Solid gold wears but keeps its color through the full thickness.
- XRF and acid. A jeweler with an X-ray fluorescence gun reads surface composition in seconds. Set the gun to a deep reading, since a thick plate fools a shallow scan. A scratch acid test and a water displacement density test give separate answers. Density = dry weight / (dry weight minus submerged weight).
Price math
At a spot price of $3,000 per troy ounce, fine gold costs about $96 per gram. An 18k case that holds 52.5 grams of fine gold carries about $5,060 in metal. Asking prices far under scrap value for a solid gold IWC point to a coated case.
Plating terms in US trade rules
US jewelry guides set minimums for gold terms. Gold plated means a gold layer of at least 0.5 microns over base metal. Gold filled means a gold layer of at least 1/20 of the total weight. Vermeil means 2.5 microns of at least 10k gold over sterling silver. None of these terms match a solid 18k IWC case, so a listing that uses them describes a different product.
What a photo cannot show
Photos do not show weight, plating thickness, or the inner caseback. Ask for a photo of the case on a gram scale, a close shot of the hallmark with the dog head, and a photo of the movement with the reference and serial numbers. Send those images to IWC or a watchmaker for a check against the reference file.