Short answer

33672 is not a Cartier reference number. Cartier codes its Ballon Bleu de Cartier models in a W-prefix format, so the 42mm steel automatic is W69012Z4 and the 33mm steel quartz is W6920084. A bare five-digit number in a product listing is almost always the seller's own stock code, and it often borrows digits from the case back of a real watch. The number tells you nothing you can verify. So when you search that phrase, you are looking at a replica Ballon Bleu, and the only things worth judging are the size, the movement inside, and the finishing details below.

What the number does and does not tell you

Sellers reuse numbers because they need a SKU that survives a listing change, a supplier switch, or a photo reshoot. That is the whole function. It does not map to a diameter, a dial color, or a movement. If a listing leans on "33672" as proof of a specific model, treat that as marketing copy. The specs that matter are printed in the same listing in plain language: case size, movement type, bracelet or strap. Read those instead.

The five places a replica Ballon Bleu shows itself

1. The crown and its guard

The Ballon Bleu is built around a crown set into a curved guard that flows out of the case at 3 o'clock. On a real one the blue cabochon, a synthetic spinel, sits low and flush, and the guard reads as one continuous polished curve with no seam or weld line. On fakes the cabochon is often a piece of glass or acrylic that sits proud of the metal, darker or flatter than the deep blue Cartier uses. Run a fingernail around the guard and you can feel where the parts were joined.

2. The dial

Genuine dials carry a fine guilloché pattern with sharp printed Roman numerals and heat-blued steel sword hands. Replicas usually show a shallower stamping that looks like a decal under angled light, thicker numerals, and hands that were painted blue rather than blued, so they read purple or flat navy. Cartier uses IIII rather than IV at the four position. Check the gap between the minute track and the crystal edge. On many fakes the dial is a hair too small for the case, which leaves a wide ring of empty metal.

3. The crystal

Sapphire with anti-reflective coating on both faces is standard, and the tell is a faint blue or purple reflection at an angle. Plenty of replicas ship with mineral glass or a single coated lens. That glass collects scratches within months, and the coating wears into a smeary patch right where you look at the dial.

4. The case back

Engraving on a genuine back is deep and crisp, with the reference, the serial, and a short case code. Fakes are laser etched, so the lettering sits shallow and slightly frosted, and the spacing drifts between lines. Stamped backs from the same factory rarely match each other, which is useful if you are comparing two photos side by side.

5. The movement

This one you can settle without opening anything. The 42mm and 36mm Ballon Bleu are automatic, so the seconds hand sweeps. The 28mm and 33mm are quartz, so the seconds hand ticks once per second. A large case listed with a ticking seconds hand is a quartz movement in a case Cartier never built that way. With a watchmaker's help you can go further. The real calibres are Cartier 049, a modified ETA 2892, and the quartz 057. Replicas use low grade clones, and the rotor engraving is where they give up.

Size first, then everything else

Cartier builds the Ballon Bleu in 28, 33, 36 and 42mm, all close to 10mm thick and rated to 30m. Establish which one you are looking at before you compare anything. A 42mm on a 6.5 inch wrist wears nothing like a 33mm, and most listing photos are shot on a cushion or a stand that hides the proportions completely.

What breaks first on a replica

• Crown threads strip, then the watch stops keeping water out at all.
• Plated cabochons cloud or fall out of the guard.
• Bracelet screws work loose, because the threads are cut shallow.
• Rotor bearings get noisy within a year of daily wear.

The part most guides skip

Counterfeits are trademark infringement, and that is not a technicality. Richemont, Cartier's parent company, treats counterfeit goods as outside its service network. No boutique and no authorized service center will touch the watch, and an independent watchmaker cannot order the correct parts for it. Resale value is close to zero because the watch cannot be authenticated. If you buy one with that understood, fine. Go in knowing that the number in the listing is a seller's label and not a specification, and judge the watch on the dial, the crown, and the movement you can actually see.