Answer first: a fake Ballon Bleu 36mm is worth buying only when it matches the genuine case measurements (about 36.6 mm wide and 12.05 mm thick), runs a credible automatic movement, and copies the crown cabochon and dial texture with care. Boxes, papers, and seller claims matter far less than those three points.
What the 36 in the Name Means
Ballon Bleu cases run from 28 mm to 42 mm, and 36 mm sits in the middle of the range. Cartier publishes the 36 mm automatic at 36.6 mm in diameter and 12.05 mm thick, with 30 m water resistance and a crown set with a synthetic blue spinel. A listing that calls a watch 36 mm but measures 38 mm across or 10 mm thick is selling a different case. Ask for caliper photos with the crown left out of the measurement before you send money.
Prerequisites
- The exact reference number you plan to match, since dial, bracelet, and case back change between steel, two tone, and leather versions.
- Digital calipers that read to 0.01 mm.
- A 10x loupe and a bright lamp you can tilt.
- A kitchen scale for comparing watch head and bracelet weight.
- Photos of a genuine 36 mm from a dealer listing or auction archive.
- A budget that leaves room for a service if you intend to wear it often.
How to Check a Fake Ballon Bleu 36mm
- Write down the reference number you are matching, then compare the seller photos only against that one reference.
- Measure the case across the bezel with the crown excluded, and confirm 36.6 mm.
- Measure case thickness from the crystal top to the case back, and confirm about 12.05 mm.
- Inspect the crown cabochon, which should be a domed deep blue spinel seated inside the curved crown guard.
- Run a fingernail along the joint between the bezel and the crown guard, and reject any step, gap, or rough edge.
- Tilt the dial under the lamp and look for concentric rings that shift tone as one unit, not a flat printed pattern.
- Read the numerals and hands up close, checking Roman numerals with IIII at four and blued sword hands with clean bevels and no burrs.
- Turn the watch over and check the engraving, which should be sharp and readable, with reference and serial numbers cut clean.
- Weigh the head and the bracelet against a known figure for the same configuration to catch hollow cases and light links.
- Work the crown through both positions and wind it, then reject gritty or loose action.
- Get the water resistance claim in writing, and treat even a stated 30 m as splash resistance only.
Movements You Will Find
- Cartier calibre 076, based on the ETA 2892-A2, about 3.6 mm thick, 28,800 vibrations per hour, with roughly 42 hours of reserve. This is what a genuine 36 mm automatic carries.
- Miyota 9015, a common stand in, thin and reliable, with a smooth sweep.
- ETA 2824 clones, about 4.6 mm thick, which can push total case thickness above the genuine figure.
- Engraved 076 clones, where the plates carry Cartier script. Spin the rotor by hand and listen for scraping.
Red Flags
- Case dimensions off by more than 0.3 mm in either direction.
- A cabochon that is flat, cloudy, or glued above the crown guard instead of seated inside it.
- Roman numeral four shown as IV instead of IIII.
- Dial texture that looks printed under a loupe.
- Soft or shallow case back engraving.
- A seller who will not send caliper photos or a movement shot.
After You Buy
- Have a watchmaker open the case, check the gaskets, and confirm the movement is lubricated.
- Keep the watch out of showers, pools, and the ocean regardless of the rating.
- Schedule a service every three to five years if you wear it daily.
- Store it on a soft surface so the cabochon and crystal are not resting against metal.