Short answer
Reference 33681 turns up on the caseback of a Cartier Ballon Bleu, and in the replica trade it is shorthand for the 36mm steel automatic, the mid-size model that sits between the 33mm and the 42mm. A "replica 33681" is a counterfeit of that watch. Prices run from about $30 for a quartz copy to $400 and up for a version with a cloned Swiss-pattern movement, and the quality gap inside that range is wider than most buyers expect.
Where the number comes from
Cartier stamps a case reference on the back that is separate from the retail model code, the W69012Z4 style string you see on a boutique tag. Sellers blend the two, which is why listings for a "33681" sometimes describe a 33mm case and sometimes a 42mm. Collectors generally read the five-digit stamps as a case-generation marker, and the 36mm steel automatic is the one most people mean when they type that number. If a seller cannot tell you the case diameter and the movement in the same message, the number on the listing means very little.
What the genuine watch does
The Ballon Bleu arrived in 2007 and became one of Cartier's best sellers on the strength of one detail: the crown, set inside a curved flank of the case with a blue sapphire cabochon on top, so it looks like a balloon tethered to the side of the watch. The dial carries Roman numerals and a guilloché texture, the hands are blued steel, and the 36mm automatic runs a date window at 3 o'clock. Case finishing is a mix of polished and brushed surfaces that catch light at different angles, and the bracelet uses screws rather than pins on most versions.
How the copies split into tiers
- Under $60: quartz movement, brass or zinc case, plated finish, cabochon in molded plastic. The seconds hand ticks instead of sweeping.
- $120 to $250: Chinese automatic in the 2824 or 2892 layout, sapphire crystal on better examples, cabochon in low-grade synthetic stone. Case proportions often run thick at the lugs.
- $300 to $500: tighter case geometry, anti-reflective coating, correct hand stack, engraved caseback with real depth to the lettering. The movement is still Asian. A "Swiss made" stamp on the rotor does not make it Swiss.
What I look at first
- The cabochon. It should be a dome, not a flat disc, and the blue should read as deep sapphire rather than candy blue.
- Dial printing. Roman numerals on a cheap copy look slightly fuzzy at the edges and the guilloché pattern is stamped shallow.
- Caseback engraving. Sharp, even depth. Soft or shallow lettering is the fastest tell.
- Crown feel. Winding should have resistance, and the date should flip within a few minutes of midnight, not drift across an hour.
- Weight. A plated brass case feels hollow in the hand compared with steel at the same size.
- Bracelet screws and end-link fit. Gaps at the lugs are common on mid-tier builds.
What the listings leave out
US Customs and Border Protection seizes counterfeit watches as trademark-infringing goods, so a shipment can be lost with no refund route. There is no warranty, no service network, and no parts supply, which means a broken movement is a paperweight. Water resistance claims are almost never tested, so keep any replica away from pools and showers. Resale value is close to zero, and many marketplaces will pull a counterfeit listing on sight. You are buying a look, not an asset.
A fair alternative
If the shape is what draws you in, several independent brands make legal homage watches with the same rounded case and cabochon crown idea for the price of a top-tier copy. A pre-owned genuine 33mm quartz Ballon Bleu also lands in the same range as the most expensive replicas, and it keeps its value, its service history, and its resale paperwork. That is the option I would point a friend toward.