Short answer
A fake Ballon Bleu 33708 is almost always a steel Cartier Ballon Bleu de Cartier in the 33 mm case, and "33708" is a dealer or auction stock number, not a Cartier reference. Genuine Cartier references follow the W-prefix format, such as W69012Z3 or W6920071. If a seller cannot tell you which number is the reference and which is their own inventory tag, treat the watch as unverified until you handle it. The checks below take about twenty minutes and catch most replicas.
What the number 33708 usually means
Stock numbers get recycled. The same digits can appear on a different watch from a different seller six months later. Use the number only to identify the listing you are looking at, then confirm the real reference, case size, and movement from the caseback and from Cartier's own published specs.
Prerequisites
- A 10x jeweler's loupe
- Digital calipers that read to 0.01 mm
- A small digital scale
- Cartier's published specs for the specific reference you are checking
- A watchmaker or Cartier boutique willing to open the caseback
How to check a Ballon Bleu 33708 step by step
- Ask the seller to write down the Cartier reference and their own stock number in the same message, so you can see which is which.
- Measure the case across the widest point with calipers and compare the reading to Cartier's published diameter for that reference.
- Measure the case thickness at the center of the caseback and compare it to the published figure.
- Examine the crown guard arch with the loupe and confirm the steel is one continuous curve with no seam where it meets the midcase.
- Look at the crown itself, which should be fluted with an even number of ridges and set with a smooth blue cabochon.
- Tilt the dial toward a light source and check that the guilloché lines are concentric and evenly spaced across the whole surface.
- Study the Roman numerals at 10x and confirm the edges are sharp and the printing sits flush on the dial, with no halo around the characters.
- Check the sword hands from the side, since genuine blued steel is polished to a mirror finish on every face, including the underside.
- Read the caseback engravings under magnification and confirm the reference, serial, and Swiss Made marking are cut into the metal rather than printed or laser-frosted.
- Weigh the complete watch on the head and compare the figure to the published weight for that reference and bracelet type.
- Wind the watch through a full power reserve and note whether the crown turns with even resistance and seats at each position without wobble.
- Set the watch down for twelve hours and record the timekeeping error against a known reference clock.
- Have a watchmaker remove the caseback and photograph the movement, the rotor engraving, and the jewel settings.
- Take the watch and the photographs to a Cartier boutique or an authorized service center for a written evaluation.
Red flags that end the inspection
- The seller refuses to state the reference in writing before payment
- The caseback serial returns no record from Cartier
- Engravings show a grey, frosted surface instead of cut metal
- The crown cabochon is plastic, cloudy, or glued proud of the setting
- The bracelet end links rock against the case when the watch is held by the head
- The movement is a quartz caliber in a case that should hold an automatic
- Paperwork lists a reference that does not match the caseback
If you only do one check
Open the caseback. Replica Ballon Bleu watches at the 33708 price point rarely carry a movement that matches the finishing, engraving, and jewel layout of the genuine caliber, and the difference is visible in seconds under a loupe. Case dimensions and dial printing can be copied to a convincing standard, but movement finishing almost never is.