A genuine Cartier Tank Must runs on a quartz movement inside a rectangular steel case, carries a sapphire cabochon crown, and shows crisp, deep engraving on the caseback. Fakes miss at least one of those points. Measure the case against the official spec first, then check the crown, dial print, hands, and engraving. Most counterfeits fail two or more checks in under five minutes.
Prerequisites
- 10x jeweler loupe
- Digital calipers
- Kitchen scale accurate to 1 g
- The Cartier spec sheet for the exact reference you are inspecting
- Photos of a known genuine example shot at the same angle
Step-by-step authentication
- Measure the case with calipers. The Tank Must small model runs 29.5 x 22 mm and the large model 33.7 x 25.5 mm. Counterfeits drift 1 mm or more, and the case sides look thicker than the genuine profile.
- Weigh the watch. A steel Tank Must small on a leather strap lands near 30 g. A fake that feels dense or hollow points to a different case material.
- Inspect the crown under the loupe. The genuine cabochon is a domed synthetic blue spinel set in a fluted crown. Fakes show a flat top, a plastic-looking bead, or a crown that sits off-center.
- Read the dial print at 5x. Genuine Roman numerals sit sharp and even, with no ink bleed into the white or black lacquer. Blurred numerals, uneven spacing, or a printed minute track that stops short are tells.
- Check the hands. The Tank Must uses blued steel sword hands with clean edges and a flat finish. Fakes often show painted hands or a purple tint instead of deep blue.
- Hunt for the secret signature. A genuine Tank Must hides the word CARTIER inside the VII numeral. It takes magnification to see, and most fakes skip it or print it as a smudge.
- Flip the watch over. Caseback engraving on a genuine piece is cut deep with tight letter spacing, and the reference and serial numbers sit on separate lines. Laser-etched or shallow engraving is a fail.
- Inspect the strap or steel bracelet. Genuine leather is firm with even stitching, and the folding clasp carries a clean Cartier signature. Loose stitching, glue residue, or a stamped logo mark a fake.
- Cross-check the reference number on the caseback against the Cartier spec sheet for case size, dial color, and bracelet type.
Tank Must is a watch, not a bangle
Search traffic for a "Tank Must bangle" mixes two product lines. The Tank Must is a wristwatch. Cartier bangles belong to the Love and Juste un Clou lines, plus older Must de Cartier jewelry pieces. When a listing calls an item a "Tank Must bangle," ask for the exact product name and reference. A seller who cannot name the line is a seller to skip.
Vintage Must de Cartier versus the modern Tank Must
The 2021 Tank Must relaunch is a quartz steel watch with a sapphire crystal. The older Must de Cartier line from the 1970s to the 2000s used vermeil cases and different dial layouts. Compare a candidate against the correct era. Mixing specs across generations produces false alarms and missed fakes.
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Common failure points
- Case thickness above or below the published figure
- Flat or cloudy cabochon
- Soft dial print and uneven numeral spacing
- Missing secret signature in the VII
- Shallow caseback engraving with wrong font weight
- Generic quartz movement visible through an opened back