The short answer
Cartier does not make a 23mm Ronde. The Ronde Solo is sold at 29mm, 36mm and 42mm, and the Ronde Louis Cartier comes in 29mm and 36mm. A listing that says "replica Cartier rotonde 23mm" is almost always one of three things: a mislabeled small case, a generic quartz ladies' watch dressed with a Cartier dial, or a seller rounding a 24mm or 25mm case down to make it sound daintier. What you are really shopping for at that size is a small quartz dress watch, not a scaled-down clone of a real reference.
Where the 23mm number comes from
Small Cartier cases do cluster in that range, which is why the number feels plausible. The Panthère de Cartier small sits around 22mm across depending on the year. The Tank Must small measures roughly 29.5mm by 22.5mm. A small Tank Française lands near 25mm wide. Sellers borrow the Ronde name because it sounds more formal than "Tank," then borrow a Panthère or Tank case to match the number they printed.
If you measure a genuine small Cartier on a caliper, you will get a length and a width, not one round figure. A single number like 23mm is a hint that nobody measured anything.
What sits inside a small replica
- Movement: a quartz caliber, usually a Swiss Ronda or a Chinese equivalent. Small round cases rarely fit a decorated automatic, so "Swiss super clone" language does not apply at this size.
- Case: 316L stainless steel. Two-tone versions use gold plating measured in microns, and it wears through at the crown and lugs first.
- Crystal: sapphire on the better ones, mineral glass on the cheap ones. You cannot tell by looking, only by scratching.
- Dial: the Ronde is a printed Roman numeral dial with a rail track. At 23mm the printing gets crowded, and that is where fakes show themselves first.
- Crown: genuine pieces use a blue spinel cabochon. Replicas use glass, dyed synthetic, or a plastic bead that goes cloudy in sunlight.
How it actually wears
23mm reads as a vintage or ladies' dress size. On a 7-inch wrist it looks like a coin sitting on a table. On a 5.5-inch wrist it looks correct. That is the whole point of the size, and it is also why the resale pool is thin.
The legal part people skip
Trademark counterfeiting is a federal crime in the United States under 18 U.S.C. 2320. Customs and Border Protection can seize and destroy a shipment, and they do not need a commercial quantity to act. Buyers occasionally get a seizure letter for a single watch. Reselling moves you from possessing an infringing item into trafficking, which is where the real penalties live. Brand holders rarely sue individuals, but they sue sellers constantly.
Do the math before you commit
At 23mm, a high-tier replica often costs close to a genuine vintage Cartier quartz in steel, or a new entry-level quartz from a brand nobody will question. A real watch holds some value and can be serviced. A fake at that size holds nothing and cannot be repaired at a Cartier boutique.
What to check on any small Cartier-style watch
- Ask for a measured width with calipers, not the listing text.
- Request a macro photo of the dial printing at 12 o'clock. Crooked numerals and a broken rail track are the giveaway.
- Look at the cabochon in daylight. Genuine spinel stays deep blue; glass goes milky.
- Compare the caseback engraving to the reference number the seller claims. Generic text or a mismatched number means a generic case.
- Ask for movement photos. A quartz watch has a battery hatch or a snap back, and the movement will be stamped.