Short Answer

A fake Breguet Type XXI 3817 is a replica of a 42 mm steel flyback chronograph that Breguet builds in small numbers. Replicas come in three tiers: a cheap quartz lookalike, a mid-tier automatic with a decorated generic movement, and a top-tier clone that copies the case and dial. None of them reproduce the movement architecture, the dial furniture, or the hand finishing of the real watch. You can place a specific replica in a tier in about ten minutes with calipers, a loupe, and a few function tests.

Prerequisites

  • Digital calipers or a machinist's rule
  • A 10x loupe and a bright, angled light
  • High-resolution photos of the dial, caseback, and movement from the seller
  • The manufacturer spec sheet for the exact reference number you are comparing

What the Genuine Reference Is

The Type XXI 3817 belongs to a line Breguet developed from French naval aviation chronographs of the 1950s. The modern reference uses a 42 mm steel case, a sapphire crystal, a screw-down crown, an automatic movement with a flyback chronograph, a 24-hour day and night display, and a date window. Water resistance is rated for swimming, and the watch ships on a leather strap. Because the model is not a mass-market shape, replica makers work from photos rather than from a stripped genuine watch, which is why proportion errors show up so often.

How to Inspect a Fake Type XXI 3817

  1. Confirm the reference number on the caseback against Breguet's published spec sheet for that number.
  2. Measure the case across the bezel at 3 and 9 o'clock and compare the result with the published diameter.
  3. Measure case thickness from the back of the caseback to the top of the crystal.
  4. Check lug width and the distance between the lugs with the strap removed.
  5. Look at the crystal edge under the loupe for a domed profile and an even anti-reflective tint.
  6. Inspect dial printing with the loupe and check letter spacing, stroke weight, and the alignment of each marker.
  7. Compare the subdial positions with spec photos and measure the gap between them.
  8. Run the chronograph, then press reset while it is running to see whether the flyback returns in one motion.
  9. Time the chronograph seconds hand against a known 60-second reference to check the beat rate.
  10. Turn the crown through the date change and the day and night indicator, and watch for a soft or grinding feel.
  11. Photograph the caseback engraving at an angle and compare depth, font, and spacing with reference images.
  12. Ask for a photo of the movement and compare rotor engraving, bridge finishing, and jewel count with the genuine caliber.
  13. Request a timegrapher printout showing rate, amplitude, and beat error.

Tells Most Replicas Fail

  • Case thickness runs high because movement spacers add depth.
  • Dial printing shows uneven ink, and markers miss the minute track.
  • Pushers feel loose, and the flyback reset catches instead of snapping back.
  • Engraving on the caseback is shallow and lacks the crisp edge of a stamped or laser-cut original.
  • Movement finishing shows unpolished screws and a rotor with flat, printed text.
  • Strap leather and buckle hardware use stamped steel rather than milled components.

Legal Note

Counterfeit watches carry protected trademarks, and selling them is illegal in the United States. Buying one for personal use still means owning a product that the brand will not service and that cannot be resold as genuine. Treat any listing that calls a replica "1:1" or "Swiss made" with caution.