The short answer
A fake Cartier Tank Must Large is a copy of a steel quartz watch that Cartier sells for just over $3,000. There is no authorized replica market and no factory building them to Cartier's standard. Fakes run from $60 throwaways to $400 "super clone" builds, and the gap between those and the real watch shows up the second you hold one under a loupe or try to get it serviced.
What the genuine Tank Must Large is
Cartier brought the Must line back in 2021, and the Large is the middle size in that family. The case measures about 33.7 mm by 25.5 mm and sits roughly 6.6 mm thick. It runs on quartz, which is why it stays so thin. Steel case and caseback, sapphire crystal on the current generation, a blue synthetic spinel cabochon in the crown, and a leather strap. Roman numerals, blued sword hands, and Cartier's hidden signature tucked inside one of the numerals.
That spec sheet is the benchmark every replica gets measured against.
Where replicas give themselves away
Case and crown
Replica cases almost always run thick. A millimeter and a half sounds like nothing on paper, but the Tank is a flat rectangle, so extra depth reads clearly in photos and feels wrong in the hand. The crown is the second tell. The genuine cabochon is a smooth domed spinel that catches light evenly. Copies use glass, dyed plastic, or a stone glued in with visible adhesive. Crown threading feels gritty, and the crown often sits proud of the case instead of flush.
Dial and hands
Print quality separates the grades more than anything else. On the real dial the Roman numerals are sharp, the minute track is even, and the black is dense. On copies, look for fuzzy edges, numerals that sit slightly off the vertical, and a hidden signature that is missing or drawn as a smudge. Blued hands on a replica are usually painted, so the color reads flat blue instead of dark steel that shifts with the light.
Movement and crystal
Most replicas run a generic quartz module, often a Miyota or an unbranded Chinese unit. It will keep time. It will also be the first thing to fail, and nobody stocks parts for it. Mineral glass instead of sapphire is common at the low end, and it scratches within months.
Why "Swiss made replica" is a marketing phrase
Sellers like the phrase because it sounds reassuring. In practice, the overwhelming majority of these watches are assembled in China. A few high-end operations drop in a Swiss quartz module or a Swiss ETA automatic, but that does not make the watch a Cartier and it does not make it legal to import. Photos are a separate problem: most listings use stock images of the genuine watch, so what arrives never matches what you saw.
The part buyers tend to skip
- Federal law treats trafficking in counterfeit goods as a crime under 18 U.S.C. 2320, and that covers selling, not just manufacturing.
- Customs and Border Protection pulls counterfeit watches out of mail and courier shipments. You can lose the watch and the money.
- Cartier will not service a counterfeit, and plenty of independent watchmakers will not either once they open the caseback.
- Resale value is effectively zero. There is no secondary market for fakes beyond other people buying fakes.
- Water resistance claims mean nothing. Gaskets on cheap copies are often dry or missing.
How to spot one in the wild
Hold it. Weight is the fastest check, because a thin steel case around a proper quartz movement has a density a chunky copy does not match. Then look at the crown stone, run a fingernail along the case edge for sharp machining, and read the caseback engraving. Genuine engraving is crisp and consistent. Replica engraving looks shallow and dotted, and the reference numbers often match no Cartier reference at all.
If a Tank Must Large is priced under $1,000, you already have your answer.