Short answer
A replica Cartier yellow gold watch is a copy with a gold-colored finish. It is not solid 18k gold. Most replicas use gold plating between 1 and 5 microns thick over a brass or steel case. A small number of sellers claim solid gold. Ask for two numbers before you pay: case weight in grams, and plating thickness in microns.
What yellow gold means on a replica
Cartier makes yellow gold watch cases in 18 karat gold, stamped 750. That alloy is 75 percent gold. Solid 18k gold has a density of about 15.5 g/cm3. Stainless steel sits near 7.9 g/cm3. A solid gold case of a given size weighs about twice what a steel case of the same size weighs.
Replica makers use three finishes:
- Gold flash: under 0.5 micron of gold. Wears through in months on a case that rubs a cuff.
- Electroplated gold: 2 to 5 microns. Common on mid-tier replicas.
- PVD coating: titanium nitride or a gold-colored compound. Hard film, but it holds no gold.
Check the case weight
Ask for the weight of the head only, without the strap. A steel case at 40 mm weighs about 50 to 60 g. A solid 18k case at the same size adds a large share of that again. A seller who lists 70 g and calls the case solid gold has a number that does not fit.
Density is the test you can run at home with a scale and a cup of water. Plated steel and solid gold do not land in the same range.
Hallmarks and stamps
Cartier stamps 750 or Au750 on gold pieces, plus a maker mark and a serial. Replica cases carry the same stamps. A stamp proves nothing on its own because stamps are copied. French eagle-head hallmarks for 18k gold appear on replicas too.
Plating life and re-plating
A 3 micron gold plate on a watch case lasts about 1 to 3 years with daily wear. Contact points go first: caseback edges, crown, lugs, and the clasp. Re-plating a case costs money and needs a plater who strips the old layer first. PVD films last longer but cannot be touched up at home.
Legal status in the US
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320. CBP can seize counterfeit shipments at the border, including single items bought for personal use. A seller who labels a plated watch as solid gold also faces deceptive-practice claims under FTC rules.
Questions to ask a seller
- Case weight in grams, head only.
- Plating thickness in microns, and the plating method.
- Base metal of the case: brass, 316L steel, or something else.
- Return window in days, in writing.
- Strap material and whether the clasp is plated.
What stays unknown
Plating thickness claims are hard to check without lab tools. Most listings do not publish microns. Treat an unstated figure as thin. Gold color also varies by alloy batch, so a photo is not a color match.