We Open the Case Back First: How We Spot a Fake Passed Off as Genuine

At ONE OF ONE, every watch we purchase goes through the same first step: we look inside. A dial can be reprinted and a bracelet can be swapped, but a movement is much harder to fake convincingly.

Recently, a customer came to our store asking us to buy a Cartier Ballon Bleu (28mm, stainless steel, black leather strap). From the outside, it looked right: the Roman numerals, the blue cabochon crown guard, the “CARTIER” signature, everything in place. The story changed once we opened the case back.

1. The movement is the most honest part

A genuine quartz Ballon Bleu runs on a Swiss caliber specified by Cartier. The movement in this watch carried generic markings that did not match what Cartier uses, along with text pointing to a different place of manufacture. A mismatched movement is the most reliable red flag, and no amount of exterior polish can hide it.

2. A genuine serial number doesn't make a watch genuine

The case back carried a reference number, a serial-style number, and the engravings “Stainless Steel” and “Swiss Made.” Under magnification, the engraving itself was clean. More surprising: when we registered this serial number on Cartier's official website, the registration went through without any problem.

Many people believe that if a serial number registers on Cartier's website, the watch must be genuine, and they stop checking there. Counterfeiters are counting on exactly that. If a real serial number from an authentic watch is engraved onto a fake, it passes the website registration step. A real number does not make a real watch, which is why a fake carrying a genuine serial number is the most dangerous kind.

In cases like this, you have to look at the watch itself, not just the number. The movement, the finishing inside the case, and how the parts fit together are things a copied serial number cannot reproduce. They are what ultimately decide authenticity.

3. Small details add up

We found rough finishing and signs of corrosion inside the case, a movement that looked fitted into the case rather than built for it, and strap lining markings that differ from Cartier's usual style. None of these alone is conclusive. Together, they paint a clear picture.

Our verification process

We inspect the dial, hands, crown, and case back under magnification, identify the movement's caliber and markings, and cross-check the serial and reference against Cartier's registration.

Trying to sell a fake as genuine is a crime

Knowingly attempting to sell a counterfeit as the real thing can be punished as attempted fraud under Korean law, even if no payment is ever received. Selling goods bearing a counterfeit trademark is also a violation of the Trademark Act. When a fake is identified during our purchase process, we decline the purchase, and the cost of the authentication is billed separately. Some watch businesses go further and charge a penalty of a percentage of the watch's price when a fake is caught.

Want to sell a genuine watch?

If it's genuine, you have nothing to worry about. We will verify it carefully and pay promptly.

We're at 336 Apgujeong-ro, Unit 109, Seoul. Please contact us at +82 10-8995-7062.