Short answer
The number 4046 is stamped on the case back of a Rotonde de Cartier. It is a case number. It is not a full model reference. Cartier model references start with W or CRW and carry seven digits after the prefix. Replica sellers copy the 4046 stamp and the dial text. Most do not copy the movement.
What the 4046 case number covers
Cartier uses four-digit case numbers to track case production. The same case number appears across a run of watches. Cartier pairs it with a movement number on the bridge and a separate serial number. A seller who shows no movement photo has shown nothing.
Rotonde de Cartier cases measure 40 mm and up. Many models use the Cartier 1904-PS MC automatic, a 27-jewel movement with a 48-hour power reserve. Other Rotonde models add a chronograph module or a tourbillon carriage. Check the caliber number against the case number before you buy.
Where fakes fail
- Movement. Replicas use a third-party automatic, often a Seagull or Miyota base. Rotor engraving is shallow. The Cartier script is stamped, not cut in relief.
- Hands. Genuine hands are polished steel or blued steel. Replica hands show paint, rounded tips, and uneven lume.
- Dial. Rotonde dials with engine-turned patterns show cut lines under 10x magnification. Printed copies look flat.
- Crown. The cabochon is a blue spinel set in a metal collet. Replicas use dyed plastic or glass in a glued seat.
- Case back. Laser engraving leaves a raised edge and dark fill. Genuine engraving is cut and even in depth.
Checks you can run in two minutes
- Ask for a photo of the case back at 10x. Read the case number, movement number, and serial.
- Ask for a movement photo with the rotor turned. Compare the bridge shape with the 1904-PS MC.
- Weigh the watch. Record the number and compare it with published specs for that case size.
- Check the crown. A cabochon that spins in its seat or sits proud of the metal is wrong.
- Look at the strap. Cartier alligator straps carry a heat stamp and a stitched keeper.
Price signals
Replica listings for a Rotonde 4046 run from about $60 to $400. Genuine steel Rotonde watches trade in the four-figure range used, and gold models run higher. A steel Rotonde with box and papers at $500 is not a bargain.
Limits of any check
A photo set cannot prove a watch. A watchmaker with a case-opening tool and a timing machine settles the question in about 10 minutes. Cartier keeps its serial records internal, so verification runs through a boutique or an authorized service center. Pay for that step before you pay for the watch.