The round Cartier, with its certificate and box.

Cartier makes the Ballon Bleu in sizes from 28 to 42, and the small ones are quartz. The 33 is the first size with an automatic movement, the calibre 076, which is why it is the one to buy if you want a mechanical Cartier without the 36 or 42mm case. On the wrist it reads as a round watch with a thick polished rim, the crown guard flowing out of the case on the right and the cabochon sitting inside it like a drop of water.

The dial is the Cartier grammar: silver with a fine guilloche, Roman numerals with the secret signature in the VII, a railway minute track and blued steel sword hands. No date on this size. The bracelet is steel links with a hidden deployant.

Rebag gives the case at 33mm and 10mm thick, the band at 16mm, a wrist size of about six inches, steel case and bracelet, a silver dial, an automatic movement, and the condition as Good: slight scratches on the crystal, wear, moderate scratches and minor dings on the case and band. Good is Rebag’s grade below Very Good, so expect a worn watch. It comes with the certificate, the box and a dated warranty card. It does not give the reference; the 33mm steel automatic on a bracelet is W6920071 in Cartier’s catalogues and the photograph matches it. Ask Rebag to confirm from the papers.

The calibre, reserve and water resistance here are Cartier’s published figures for that reference, not measured on this unit. With the wear described, ask when it was last serviced.

This unit is sold by Rebag through Amazon Luxury Stores, authenticated by the seller with Amazon’s 30-day return window on top; it is one piece, and when it sells the listing goes away, so the second button opens the live search for 33mm Ballon Bleus.

Steel Ballon Bleus have resold for under new and close to what pre-owned buyers paid, sometimes more, sometimes less; that is a pattern, not a promise, and nothing here is investment advice.