Short answer
A "fake Drive 42mm blue" is a third-party replica of the Cartier Drive de Cartier with a blue dial. It copies the cushion case, the sunray dial, and the Roman numeral layout, but it almost never matches the real watch in four places: dial printing, case finishing, crown shape, and movement. Genuine Drive de Cartier cases measure roughly 40 to 41 mm depending on reference, so the "42mm" in a listing is seller shorthand rather than a factory number. If you are inspecting one, measure the case, read the dial under magnification, and look at the movement before you look at the price.
What the 42mm blue label actually means
Cartier sizes the Drive de Cartier line by reference, not by a single round number. The three-hand steel models sit near 40 mm across, the Extra-Flat sits smaller, and the complication models sit slightly larger. A seller who advertises a fixed "42mm" is usually repeating a supplier spec sheet, which is a small but useful signal about how much of the listing is copied text. Ask for the exact reference number and measure the case yourself with calipers across the widest point, not across the lugs.
Where replicas fail first
Dial and printing
Look at the Roman numerals at 12 and 6 and the railway minute track. Genuine printing is crisp, evenly weighted, and sits flat on the dial surface. Replica printing is often slightly thick, with filled-in counters on the numerals and a minute track that drifts out of alignment near the date window. The sunray finish on a blue dial should radiate from the center and shift color as you tilt it. Flat blue with no gradient is a strong sign of a fake.
Case, bezel, and crown
The cushion case has a mix of brushed and polished surfaces that meet on hard, clean lines. On fakes the transitions look soft or wavy, and the lugs feel thick when you run a fingernail along the edge. The crown is the giveaway most buyers miss: it should be faceted, set with a cabochon, and sit flush against the case with no gap when screwed down. Replica crowns are frequently round, oversized, or fitted with a plastic-looking stone.
Movement and caseback
Cartier uses its own in-house calibers in this line, and those movements have a specific beat rate, jewel count, and finish. Replicas typically run a generic or cloned automatic movement with a stamped rotor plate. Remove the caseback or ask for a movement photo. A rotor engraved with shallow laser text, missing perlage, or unpolished bridges points to a copy. Caseback engraving should be deep, evenly spaced, and match the reference number on the paperwork.
How to inspect one in person
- Measure the case across its widest point with digital calipers and write down the number.
- Compare that measurement and the reference number against Cartier's published specs for the same reference.
- Examine the dial under a 10x loupe and check the numeral printing and minute track for fill or drift.
- Tilt the dial toward a light source and confirm the blue shifts in tone from the center outward.
- Unscrew the crown, check for facets and a set stone, then screw it down and feel for a flush fit.
- Ask the seller for a clear movement photo showing the rotor, bridges, and jewel settings.
- Weigh the watch. A steel Drive de Cartier on a strap falls in a narrow band, and light fakes read noticeably under it.
Price, paperwork, and legal risk
Any offer far below the secondary market for a blue-dial Drive de Cartier should be treated as a replica until proven otherwise, no matter how good the photos look. Boxes and papers are easy to counterfeit, so treat them as a bonus rather than proof. In the United States, counterfeit watches are subject to seizure by U.S. Customs and Border Protection, and importing or reselling them can carry civil penalties. If your goal is to own the look, a genuine pre-owned reference or an honest homage brand keeps you out of that exposure and holds value.