Short answer
A 23mm Rotonde de Cartier does not exist. Cartier's Rotonde line is a round, large-format collection that starts around 40mm, so any listing advertising a "fake Cartier Rotonde 23mm" is describing a counterfeit case size, a small watch from a different Cartier family with the wrong name attached, or a stock photo swapped in from another model. The 23mm figure itself is the first red flag, before you inspect a single engraving.
What the real Rotonde de Cartier line actually measures
Rotonde de Cartier watches are built around round cases in men's and unisex proportions. The common references run from roughly 40mm up to 47mm, with the complicated pieces sitting at the top of that range. The design language is consistent: a round case with a fluted crown set with a synthetic spinel cabochon, a guilloché or flinqué dial, Roman numerals, and blued or sword-shaped hands.
- Rotonde de Cartier automatic and chronograph models: about 40mm to 42mm
- Rotonde de Cartier tourbillon and mystery models: about 45mm to 47mm
- No Rotonde reference in the current or historical catalog at 23mm
Which Cartier watches are actually near 23mm
Small Cartier cases do exist, but they belong to other lines. A seller who mixes these names with "Rotonde" is guessing.
- Tank Louis Cartier small: about 29.5mm by 22mm
- Panthère de Cartier mini: about 25mm by 19mm
- Baignoire: about 31mm by 23mm
Markers of a counterfeit
- Measure the case with calipers. Counterfeit listings often quote a size copied from a different model.
- Read the caseback font. Genuine Cartier engraving is sharp, evenly spaced, and consistent in stroke width.
- Check the crown cabochon. A plastic or cloudy stone points to a replica.
- Look at the dial printing. Roman numerals on fakes show uneven spacing and thick serifs.
- Ask for movement photos. Counterfeit movements are undecorated and unmarked where a genuine caliber carries finishing and a reference number.
- Request the serial and reference, then compare both against Cartier's own collection data.
Legal and resale consequences
In the United States, trafficking in counterfeit goods is a federal offense, and imports of counterfeit watches can be seized and forfeited by customs authorities. Buyers also lose everything on the back end: no Cartier service center will touch a counterfeit, no auction house will consign one, and the resale value is effectively zero. The money saved at purchase is gone the moment the watch leaves the box.
If a small round Cartier is what you want
- Decide which real line matches the case size you want, Tank, Panthère, or Baignoire.
- Buy from an authorized dealer or a seller with verifiable service history.
- Have an independent watchmaker open the case and confirm the movement before you pay.
- Keep the box, papers, and service records together. They carry most of the value.