The short answer
There is no Cartier watch called the Rotonde 4046. The phrase is a search term built from three pieces: a brand, a collection, and a number that sellers drop into listings to sound specific. Cartier's Rotonde de Cartier is a real line of round dress watches, and 4046 shows up in marketplace titles as a case code, a movement code, or nothing at all. If you landed here after seeing the term, you were almost certainly looking at a counterfeit.
The real watch in the background
Rotonde de Cartier sits at the top of Cartier's range. Round case, Roman numerals, a flinqué or guilloché dial, and an in-house MC caliber made at the brand's facility in La Chaux-de-Fonds. Many references come in solid gold or platinum, and the complicated versions run well past the price of a car. That is the context that matters, because a watch built to that spec cannot be copied for the price of a nice dinner.
Why the number keeps appearing
Numbers in replica titles are marketing filler. Sometimes they echo a genuine caliber code, sometimes a case diameter in tenths of a millimeter, sometimes a batch number from a factory that will not exist next year. Two sellers using "4046" may be selling two completely different watches. Treat any digits in a counterfeit listing as decoration, not a specification you can research or compare.
What a copy cannot fake
- Metal. The genuine article is gold or platinum. Copies use steel with plating, and the plating wears through at the lugs and crown within a year or two of daily wear.
- Dial finishing. Guilloché turned on a rose engine has a crispness that stamped or printed imitations lose the moment you look closely.
- Movement. Cartier builds its MC calibers in-house. Copies carry generic movements, often with a rotor engraved in a font Cartier does not use.
- Service. No authorized watchmaker will touch it. A mechanical watch needs servicing every five to seven years, and a counterfeit has nowhere to go.
The legal side, if you are in the US
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. § 2320, and the penalties scale with the value of the goods. Importing them is a separate problem: Customs and Border Protection seizes and destroys counterfeit shipments, and buyers occasionally get a letter instead of a watch. Civil liability under the Lanham Act can reach the purchaser in some fact patterns, though the felony exposure sits with the seller. What you definitely do not get is a warranty, a return path, or resale value. A counterfeit is worth nothing on the secondary market, and anyone who knows watches can spot one across a table.
If what you want is the look
The Rotonde's appeal is a round gold dress watch with a clean dial and Roman numerals. That look is available legally. A Seiko Presage, a Tissot Le Locle, or a vintage gold-plated dress watch from the 1960s gets you the silhouette, keeps its value better than a fake, and can be serviced by any competent watchmaker. None of them say Cartier on the dial, which is the point.
Bottom line
"Replica Cartier Rotonde 4046" describes a category of counterfeit, not a watch. The reference does not exist, the number in the title means nothing, and the object behind the listing is a steel watch with a plated finish and a movement nobody will repair. If you already own one, a local watchmaker can tell you what is actually inside it. If you are still deciding, the honest answer is that the money buys more watch elsewhere.