The short answer
A fake Cartier Tank Cintrée is a copy of a curved rectangular watch Cartier first sold in 1921. The real watch is thin, curved along its length, and made in gold or platinum. Most copies fail on three points: thickness, the shape of the curve, and the crown. A copy that measures 9 mm thick or more is not close to the original. The genuine large model is about 46 mm long, 23 mm wide, and 7 mm thick.
What the Tank Cintrée is
Cartier added the Cintrée to the Tank line in 1921. Cintrée means curved in French. The case bends along its length to follow the wrist, unlike the flat Tank Normale. The length-to-width ratio is about 2 to 1. Cartier returned to the shape for anniversary releases in 2021. Production counts for vintage pieces are not published, so auction houses and dealers rely on case numbers, hallmarks, and service records.
Case, curve, and thickness
Measure the watch before anything else. The real case is about 7 mm thick and bends on a single radius. Copies use a straight case with beveled lugs that suggest a curve, or a case bent at the wrong radius that sits off the wrist. Look at the brancards, the two vertical gold bars beside the dial. They taper toward the lugs. Copies tend to leave them parallel.
Dial and hands
Cartier dials use thin strokes and wide letter spacing. The word Cartier sits below the XII. Many Cintrées hide the word Cartier inside the numeral VII, a mark Cartier used against copies. Hands are blued steel, in a sword or apple shape by year. Classic sizes carry no seconds hand. Copies print text with thick strokes, fit chrome hands, and add a small seconds subdial the original does not have.
real cartier tank cintrée details
Crown and cabochon
The crown is spherical and set with a cabochon. Cartier uses blue sapphire or ruby. Copies use glass or plastic, with uneven color, or a flat disc. A real cabochon is domed and polished. The crown on a genuine watch seats tight against the case. Copies sit loose and turn with grit.
Movement and caseback
Vintage Cintrées are hand wound. Many 1920s and 1930s examples use movements from European Watch & Clock Co., the Cartier and Jaeger-LeCoultre joint venture. Copies use quartz or a thin automatic. Open the caseback only with a dealer present. Engraving depth, serials, and hallmarks are the strongest evidence. Swiss, French, and UK import hallmarks appear on genuine gold cases. Copies show no marks, or marks that do not match the metal.
Price and market
Genuine Cintrées trade in the five figures at auction. Rare early platinum pieces and unusual dials have sold higher. Copies sell for tens or hundreds of dollars. That gap is the simplest check. A seller offering a Tank Cintrée for $300 is not selling a Cartier. Under US law, trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320, and Customs can seize imported copies.
What photos cannot show
Photographs hide thickness and metal content. Weight, magnetism, and caseback engraving need a hands-on look. Cartier service centers do not repair counterfeits, so a copy has no service path. For a five-figure purchase, ask for written provenance and a service record.