Short answer
The number 830107 is not a Cartier reference number. Cartier Tank references follow formats such as WSTA0041 or W5200028, and older pieces use short numeric codes tied to a specific model line. A listing that labels a Tank as 830107 is using a seller's internal SKU, a factory batch code, or an invented number. Treat that as your first warning sign, then verify the watch against Cartier's published specifications for the model it claims to be.
Before you start
- A 10x jeweler's loupe
- Digital calipers or a metric ruler
- Clear photos of the front, caseback, crown and clasp from the seller
- The exact reference number the seller claims the watch carries
How to check a Cartier Tank step by step
- Look up the reference number the seller gave you. Cartier lists current Tank references on its own product pages, and dealer databases cover discontinued ones. If the number returns nothing, or returns a completely different model, stop the deal there.
- Measure the case with calipers. Compare length, width and thickness against the published spec for that reference. Counterfeits commonly run a half millimeter to a full millimeter thicker because the copied movement and caseback do not sit flat.
- Read the caseback engravings under the loupe. Genuine Cartier engraving has crisp edges, even depth and clean spacing, with a serial number and a reference number on most modern Tanks. Stamped or lazered text with rough rims, filled-in letterforms, or a missing serial is a counterfeiting marker.
- Study the dial printing. The word CARTIER should sit level, with consistent stroke weight and sharp serifs. Some Tank models hide a small CARTIER spelled into the VII numeral, but not every reference does, so confirm what your exact model should show before you judge it.
- Inspect the crown. A real Tank crown is fluted and finished with a blue cabochon set flush into the metal. Fakes often use plastic or cloudy glass that looks flat, sits proud of the crown, or shows a casting seam.
- Watch the seconds hand for a full minute. Quartz Tanks jump once per second and mechanical Tanks sweep. A watch advertised as mechanical that ticks in clear one-second steps has the wrong movement inside.
- Check the bracelet or strap hardware. Look at screw heads, end link fit and clasp engraving. Loose tolerances, uneven brushing and shallow stamping on the clasp are common on copies.
- Ask for the box, papers, warranty card and any service history. A legitimate seller can supply them or explain their absence in a way you can verify.
- Pay a watchmaker or a paid authentication service to open the caseback. A movement photo, the rotor finish and the caliber stamping settle the question faster than any external detail.
Red flags that show up on most counterfeits
- A reference number that does not exist, including 830107
- A price far below the going rate for that reference in that condition
- Blurry photos with no caseback shot and no serial number visible
- A seller who refuses to send a movement photo before payment
- SWISS MADE printed in the wrong position or missing from the dial edge
- Case weight that feels light for stainless steel or gold
If the watch fails the check
Do not send money, and do not rely on a verbal promise of a refund. Keep the listing, the photos and the messages. Report the sale to the platform, and in the United States you can file a counterfeit goods report with the Federal Trade Commission or with Customs and Border Protection if the watch ships from overseas. If you already paid, contact your card issuer or payment provider about a chargeback based on goods not as described.