Short answer
A fake Cartier gold watch is a plated copy. The base metal is brass, zinc alloy, or 316L steel. The plating layer runs 3 to 5 microns of gold. Real Cartier gold watches use 18k solid gold, or 750 parts per 1000. A plated case shows wear at the crown, lugs, and case back within months.
Hallmarks on real 18k Cartier cases
French 18k gold carries the eagle head hallmark from the French assay office. Swiss 18k gold carries the Helvetia head. The case back also holds a maker's mark and a 750 or 18K stamp. Fakes stamp 750 on the outside of the case back with no assay mark. Some fakes print 18KGP or 18K Gold Plated in small text.
- Eagle head = 750 gold, France.
- Helvetia head = 750 gold, Switzerland.
- Maker's mark sits in a rhombus or rectangle.
- No assay mark plus a 750 stamp points to plating.
Serial numbers and model codes
Cartier engraves a serial number on the case back. The number holds 6 to 8 digits, sometimes with letters. Model codes start with a letter, such as W, WG, or HP, followed by digits. The serial number and the model code are two different numbers. A fake repeats the same digits or uses a font with uneven spacing.
Cartier does not publish a full public database of serial numbers. Authentication runs through a Cartier boutique or a paid appraisal.
Movement
Cartier uses Swiss movements. In-house calibers include the 430 MC, 1847 MC, and 1904-CH MC. Gold Tank, Santos, and Ballon Bleu models run on mechanical or automatic calibers. Many fakes use quartz movements. A quartz fake has a second hand that jumps once per second. A mechanical watch has a sweeping second hand.
Weight and density
18k yellow gold has a specific gravity of 15.5. Stainless steel is 7.9. Brass is 8.4. A solid gold case weighs near twice the same case in steel. Gold-plated brass feels light for its size. A scale and calipers give a rough check. A jeweler with an XRF spectrometer gives a metal reading in seconds.
Price floors
New 18k gold Cartier watches start near $10,000 for a Tank Louis Cartier. Steel models start near $3,000. Any new 18k gold Cartier listed at $100 to $600 is not gold. Used solid gold Cartier watches sell below $4,000 in most cases.
Sales channels
Cartier sells through its boutiques and authorized dealers. Cartier does not authorize sales on auction sites, social media, or flea markets. First copy and AAAA labels come from the replica trade, not from Cartier. These labels describe plating thickness and movement grade, not gold content.
Legal status in the U.S.
Counterfeit watches fall under trademark law. 18 U.S.C. § 2320 sets a maximum of 10 years in prison for trafficking in counterfeit goods. 19 U.S.C. § 1526 lets U.S. Customs and Border Protection seize and destroy counterfeit imports. CBP publishes seizure data each year. The OECD and EUIPO report that counterfeit goods made up 3.3% of world trade in 2016. Watches rank among the top categories.
Tests a jeweler runs
- XRF spectrometer: reads the metal alloy on the surface and below the plating.
- Acid test: nitric acid on a scratch mark. Gold resists. Brass turns green.
- Magnet test: gold is non-magnetic. Steel and some alloys pull a magnet.
- Magnification: reads hallmark depth, font, and laser engraving.
- Movement inspection: identifies the caliber and the country of origin.
Fake tells
- 750 stamp with no assay office hallmark.
- Plating wear on the crown and case back.
- Quartz movement in a gold case.
- Case weight below 60 grams for a full gold men's model.
- Price under $1,000 for a new solid gold watch.
- Serial number font that differs from the Cartier script.
Unknown: Cartier does not publish serial number ranges by year. A serial check alone cannot confirm a watch.