The short answer
Most bracelets sold as a fake Ballon Bleu 33671 get caught on four checks: the cabochon, the metal, the clasp, and the engraving. It takes about two minutes. If one of those four fails, nothing else on the piece matters.
One thing to clear up first. Reference numbers get thrown around loosely by sellers. The 33671 stamp shows up on listings that are sometimes a bracelet, sometimes a watch, and sometimes a photo of something else entirely. Before you trust a number, check it against Cartier's own catalog or ask an authorized dealer to confirm it. If the seller can't show the number engraved on the piece in a clear photo, treat the listing as unverified.
fake ballon bleu 33671 bracelet
What the genuine bracelet is
The Ballon Bleu de Cartier bracelet is a solid 18K gold piece, most often yellow or rose, built from rounded links that echo the watch case. A blue sapphire cabochon sits at one end, cradled in a gold setting. Cartier stamps the clasp with its name, the reference, the gold purity (750, or Au750 on newer pieces), and a serial number, plus the assay mark for the country of manufacture. Older French-made pieces carry the eagle head.
How to Find the Perfect Replica Ballon Bleu 33671 Bracelet
The four checks
1. The sapphire cabochon
Look at the dome under a light. A real sapphire is a cut stone with depth. It shifts color slightly depending on the angle, and it sits in a setting that grips it at the edges. Fakes use glass, dyed resin, or a synthetic cabochon glued in place, and the dome often looks flat or sits above the gold like a bead. If a fingernail catches the seam between stone and setting, that is a bad sign.
2. Solid gold versus plating
Weight is the fastest tell. Eighteen karat gold is dense. A plated brass or steel copy feels light in the hand, and the clasp feels thin and loose for the same reason. A stamp reading 18K, 750, or Au750 proves nothing on its own, since anyone can punch those letters into a clasp. A jeweler can run an XRF scan in seconds without damaging the piece, and that gives you an actual metal composition.
3. The clasp and its fit
On the real bracelet the clasp closes with a firm, tight click and the two halves line up flush. The edges are polished rather than sharp, and the interior is finished as carefully as the outside. Copies are usually roughest here. You will see file marks, uneven gaps, a hinge that wobbles, or a closure that needs force to seat. Cartier service centers also size these bracelets with specific links. A piece that was cut and soldered back together shows discoloration and a slightly different gold color at the joint.
4. Engraving
Cartier's engraving is crisp with consistent depth, cut into the metal rather than burned or cast in. On fakes, lettering looks rounded, shallow, or filled with plating, and the spacing drifts. Under a loupe, real engraving shows a clean V-shaped groove. A cast-in mark looks soft and blurred at the edges.
Price and legality
The genuine piece sells in the thousands of dollars, and secondhand prices do not fall to a few hundred. If a seller wants $150 for something described as solid 18K gold with a sapphire, the metal alone costs more than that, which answers the question without any further inspection. Counterfeit goods are also illegal to import into the United States, and Customs can seize them. Selling a copy as genuine is fraud, and buying one on purpose carries risk even when the seller never gets caught.
What I would do instead
If the goal is the look rather than the gold, no shortcut survives a jeweler's loupe, and most people who buy a plated copy stop wearing it once the plating wears through at the clasp. If the goal is the real bracelet, buy from an authorized dealer or from a seller with a documented service history, and get the metal tested before money changes hands. A ten-minute XRF scan plus a reference check with Cartier will save you from an expensive mistake.