Answer first

31610 is the case reference stamped on the back of the 42 mm Ballon Bleu de Cartier automatic. Cartier launched the line in 2007. A replica listed as 31610 should match that case: 42 mm across, near 13 mm thick, steel or gold, with an oval crown guard that holds a blue cabochon at 3 o'clock. If a seller tags a watch 31610 and lists a 36 mm case, the number and the watch do not match.

Genuine specs to match

  • Case: 42 mm diameter, 13 mm thick.
  • Crystal: sapphire.
  • Movement: Cartier caliber 049, based on the ETA 2892-A2, 28,800 vph, about 42 hours of reserve.
  • Water resistance: 3 bar, or 30 m, on the steel versions.
  • Dial: silvered opaline with a guilloche pattern, Roman numerals, blued sword hands.
  • Crown: fluted, set with a synthetic sapphire cabochon.

Movement tiers in listings

Three groups turn up under this case number.

  • Entry: a basic 21-jewel automatic at 21,600 vph, about 36 hours of reserve. The sweep looks choppy next to the real watch.
  • Mid: Sea-Gull ST2130 or a Hangzhou 6300, both built on the ETA 2824-2 layout, 28,800 vph, 38 to 40 hours.
  • Upper: Miyota 9015 at 28,800 vph, or an ETA 2824-2 or Sellita SW200.

No replica ships a genuine Cartier 049. Judge the movement by crown feel, rotor noise, and rate on a timegrapher, not by the name engraved on the rotor.

Case and crown checks

  • Cabochon: centered in the crown, no glue line, no off-axis tilt.
  • Crown guard: the arc should meet the case with no step and no gap.
  • Caseback: check engraving depth, font weight, and the screw pattern.
  • Dial: letter spacing on CARTIER, the VII numeral, and the inner minute track. Errors show at 10x.
  • Bracelet: links should move without side play. Check the clasp finish.

Price bands

Listings tagged 31610 cluster in three groups. Quartz or low-grade automatic: $80 to $180. Mid-tier 2824 clone: $200 to $400. Top tier with Miyota 9015 or Sellita: $450 to $800. Gold-plated and two-tone cases cost more than steel.

Where replicas miss

Case thickness runs 0.5 mm to 1.5 mm over spec. The guilloche is stamped, so the ridges sit shallow. Most Ballon Bleu dials carry no luminous material, and some replicas add it. End links and the deployant clasp show the widest gap in finish.

Checks before payment

  1. Ask for a photo of the caseback and the case number.
  2. Ask for a video with the second hand running.
  3. Get the size in writing: 42 mm.
  4. Get the movement name and vph on the invoice.
  5. Confirm the return window in days.