The fastest way to spot a fake Cartier Tank Must is to compare three things against the authentic reference: the case back engraving, the case dimensions, and the dial printing. An authentic Tank Must carries deep, even engraving with a matching reference and serial number, measures exactly 33.7 by 25.5 mm in the Large steel version, and shows crisp Roman numerals with the Cartier secret signature worked into the VII. Copies fail on at least one of those three points, and most fail on two.

What you need before you start

  • Calipers or a digital ruler that reads to 0.1 mm
  • A 10x jeweler's loupe
  • A kitchen scale accurate to 1 gram
  • Seller photos of the case back, dial, crown, and guarantee card
  • The reference number for the size and finish you are inspecting

Step by step: how to check a Tank Must

  1. Write down the reference number first. Steel Tank Must references begin with WSTA, for example WSTA0041 on the Large steel model and WSTA0042 on the Small. Ask the seller for the number before you look at anything else.
  2. Measure the case. The Large steel Tank Must is 33.7 mm by 25.5 mm. The Small is 29.5 mm by 22 mm. The XL is 41 mm by 31 mm. Case thickness on the steel quartz models sits near 6.6 mm. A copy that runs 1 to 2 mm off is a copy.
  3. Read the dial through the loupe. The Roman numerals should have clean, filled strokes. The railroad minute track should run unbroken around the dial. The word CARTIER appears inside the strokes of the VII on most Tank references. Blur, broken lines, and floating text are tells.
  4. Check the crown. The cabochon is a blue synthetic spinel cut as a smooth dome and set flush with the crown head. Fakes use glass or plastic. The dome sits too tall, or shows bubbles under the surface, or reads a flat navy instead of a deep blue.
  5. Inspect the crystal. The authentic crystal is sapphire and sits flush with the bezel. Sapphire resists scratches. Mineral glass copies show hairline scratches within days of wear.
  6. Weigh the watch head on the scale and compare it with a known authentic of the same size. Copies run light because the case walls are thinner and the steel is a lower grade.
  7. Examine the case back engraving. The reference number, serial number, Swiss Made marking, and water resistance rating should be cut deep and centered. Shallow laser etching, uneven spacing, or a serial that does not match the papers means the watch is not authentic.
  8. Confirm the movement. The steel Tank Must runs a Cartier quartz caliber with the Cartier name printed on the movement plate. Have a watchmaker open the back unless you have the correct tool and a clean bench.
  9. Verify the paperwork last. The guarantee card must show the same reference and serial number that appear on the case back. Printed numbers, mismatched numbers, or a card with no date stamp are red flags.

Common tells on low grade copies

  • Dial text that crowds the case edge or sits off center
  • A crown that will not pull cleanly to the setting position
  • Sapphire look without the anti-reflective sheen of the real crystal
  • Strap stitching that wanders, or a buckle with a stamped logo instead of deep relief
  • A case back that lists a size code which does not match the measured case

Buying a replica Tank Must

Replica Tank Must watches come in grades, and the differences show up in exactly the places listed above. Ask the seller for the case dimensions, the movement type, and close up photos of the dial and case back before you pay. A seller who cannot supply those images is not offering a top grade piece. Use the checks above to compare what you are shown against the real specifications.