Short answer
A replica Must de Cartier Tank copies one of two watches. The 1977 Must de Cartier used a vermeil case and a lacquer dial. The 2021 Tank Must uses a steel case and a quartz movement. The genuine Tank Must Large is 33.7 mm by 25.5 mm. The Small is 29.5 mm by 22 mm. A good copy matches those numbers plus the dial print, the blue cabochon crown, the four-screw caseback, and the strap hardware. A bad copy misses at least one item on that list.
Two watches share the name
Must de Cartier started in 1977 as a lower-cost Cartier line. Those cases were vermeil, a gold layer over sterling silver. Cartier brought the name back in 2021 as the Tank Must in steel. Sellers use both names for both watches. Ask the seller which watch the photos show before you compare specs.
Genuine specs to compare
Case: polished steel. Crystal: sapphire. Caseback: steel, four screws. Dial: silvered opaline, printed Roman numerals, no date. Crown: fluted steel with a blue cabochon. Water resistance: 30 m. A SolarBeat version runs on a photovoltaic cell.
Case and crown
Measure the case with calipers. Copies come in at 34 mm or 26 mm, or the lugs sit wider than the genuine. Check thickness. A quartz Tank Must is a thin watch, and thick copies show under a shirt cuff.
The crown is a fast check. The cabochon should be blue, smooth, and set flush. On cheap copies it is plastic, too tall, or the wrong blue. Crown fluting should be sharp and even.
Dial
- Roman numerals are printed, not applied. Applied numerals mean a copy of a different model.
- No date window. A Tank Must with a date is wrong.
- Print edges are sharp under a loupe. Copy dials show ink spread.
- "Swiss made" sits at 6 o'clock in small type below the minute track.
- Cartier hides the wordmark inside one numeral. Find it before you buy.
- Hands are sword shaped and sit at the correct height above the dial.
Caseback and strap
Four screws, flush with the back. Engraving is laser sharp and centered. Copy engraving is shallow or struck twice. Leather versions use an alligator strap. The buckle carries the Cartier name, cut clean.
Movement
Genuine watches use a Cartier quartz calibre. Copies use unbranded quartz, Ronda, or Miyota. Ask for a photo of the movement and a photo of the caseback reference. A seller who cannot show both is a risk.
Checklist before you pay
- Confirm the model: 1977 vermeil Must de Cartier or 2021 steel Tank Must.
- Get case measurements in millimeters from the seller, not from the listing title.
- Ask for a photo of the crown cabochon in daylight.
- Ask for a macro photo of the dial print.
- Ask for the caseback screws and engraving.
- Ask which movement sits inside.
Legal note for US buyers
US law treats trafficking in counterfeit goods as a federal crime under 18 U.S.C. 2320. US Customs can seize shipments. A replica is not a legal substitute for a genuine Cartier watch. Account for that risk in the price.
What photos cannot show
Photos do not show weight, bracelet play, or how the crown feels. Those need a hand check. Serial numbers on replicas are copied from real watches, so a matching number proves nothing about origin.