Short answer
A replica Rotonde 18k is a copy of a Cartier Rotonde watch sold with a claim of 18 karat gold. That claim needs a check. 18k gold is 75% gold by weight. A solid 18k case for a 40 mm to 43 mm round watch holds about 20 g to 40 g of gold alloy. A plated case holds a few milligrams to a tenth of a gram. Listings use the same phrase for both.
What "Rotonde" refers to
Rotonde is a round-case line from Cartier. Rotonde de Cartier models come in cases from 40 mm to 45 mm, in three-hand, chronograph, and skeleton versions. Replica listings copy the case shape, the Roman numerals, the fluted crown with a cabochon, and the caseback engraving.
What "18k" means on a replica listing
Four claims appear on listings. They are not equal.
- Gold plating: a layer of 18k gold over brass or 316L steel. Sellers quote thickness in microns. 3 to 5 microns is common.
- PVD coating: a gold-colored titanium nitride layer. No gold content.
- Gold-filled or "18k wrapped": a bonded layer measured in mils, thicker than plating.
- Solid 18k: the case is 750/1000 gold alloy. This is rare, and the price shows it.
Checks on the gold claim
- Weigh the watch. 18k gold alloy sits near 15.5 g/cm3. 316L steel sits near 7.9 g/cm3. The gap shows on a scale and in the hand.
- Read the hallmark. Solid gold cases carry a purity stamp, 750 or 18K, plus a maker mark. A stamp alone proves nothing. Copies carry stamps.
- Look at wear points. Plating thins at the lugs, the caseback edge, and the crown. A brass tone under the gold means plating.
- Ask for an XRF readout. An X-ray fluorescence test from a jeweler gives gold content in seconds and leaves no scratch.
- Compare price to metal. A 30 g solid 18k case holds about 22.5 g of fine gold. Sellers do not sell that for $300.
Specs that replica listings cite
Common movements: Miyota 9015, Seagull ST2130, Hangzhou 6460, and ETA 2824 clones. These run at 28,800 vph with a power reserve near 38 to 42 hours. Cases are 316L steel. Crystals are sapphire with an anti-reflective coating. Water resistance claims run 30 m to 50 m and are not pressure tested.
Legal position in the US
Trafficking in counterfeit goods carries criminal penalties under 18 U.S.C. § 2320. CBP can seize a shipment at the port of entry. Gold marking falls under the FTC Jewelry Guides, 16 CFR Part 23: an 18k mark requires at least 750 parts per 1000 gold, and a plated item must be labeled as plated. A seller who describes plating as solid gold breaks both sets of rules.
Questions to ask before paying
- Is the case solid 750 gold or plated? What is the plating thickness in microns?
- What metal sits under the plating?
- Which movement, and what is the beat rate?
- Is the payment refundable if an XRF test shows plating?