Direct answer
A fake Cartier rose gold watch uses a steel, brass, or zinc case with a gold layer on top. That layer runs 0.5 to 5 microns on most replicas. A real Cartier rose gold case is solid 18k gold, marked 750. Gold makes up 75 percent of the alloy by weight. Copper and silver make up the rest and give the pink color.
Marks on a real case
Cartier stamps the case back with 750, a French eagle head or Swiss Helvetia head, and a serial number. The stamping sits in the metal. On a plated fake the 750 mark sits in plating, so a 10x loupe shows steel or brass at the edges of the punch. Serial numbers on genuine watches match the papers, the movement, and the case. Fakes repeat numbers across batches. Cartier does not publish serial ranges, so a number alone proves nothing.
Weight and density
18k rose gold has a density near 15.2 g/cm3. 316L steel sits at 7.9 g/cm3. Brass sits at 8.5 g/cm3. Zamak, a zinc alloy used in cheap cases, sits at 6.6 g/cm3. A Tank Louis Cartier in rose gold with a 33.7 by 25.5 mm case weighs about 40 g on a leather strap. The same case in steel weighs about 25 g. A postal scale reads to 1 g and costs under $20.
Plating wear
Electroplated gold wears at the lugs, the crown, and the case back edges. Skin contact and sweat speed this up. A 1 micron layer on a watch worn daily shows base metal in 6 to 18 months. PVD layers run 2 to 4 times harder than electroplating. Gold filled cases carry a bonded layer of 5 microns or more.
Movement inside fakes
Cheap replicas run quartz. Mid-tier replicas use Miyota 9015, Seiko NH35, or Chinese DG2813 and 2824 clones. Cartier uses the in-house 1917 MC in the Tank Louis Cartier and quartz in the Tank Must. The 1917 MC beats at 21,600 vph. A Miyota 9015 beats at 28,800 vph. Count ticks per second: 6 ticks means 21,600 vph, 8 ticks means 28,800 vph.
Price bands
- Under $50: zinc case, quartz movement, 0.5 micron plating.
- $80 to $250: 316L steel case, 1 to 3 microns, Miyota or DG2813 movement.
- $300 to $700: thicker plating, sapphire crystal, better bracelet finishing.
A Cartier Tank Louis Cartier in 18k rose gold retails near $13,000 to $15,000. That gap is the main tell.
Tests
- Weigh the head on a postal scale.
- Check the hallmark with a 10x loupe.
- Hold a magnet to the case. Gold and brass do not stick. Steel does.
- Ask a jeweler for an XRF reading. It reports gold content in seconds and does not damage the watch.
Law
US law bars trafficking in counterfeit goods under 18 U.S.C. 2320. CBP can seize shipments at the border and destroys seized counterfeit watches. Selling a fake as real is trademark infringement and fraud.
Open questions
Factories do not publish plating thickness, case alloy, or movement grades. The numbers above come from teardowns and XRF tests posted by repair shops. Treat each listing on its own.