Judge a replica IWC IW329120 with instruments, not with seller photos. If the case diameter, thickness, and lug width sit close to the published spec, the dial text uses the correct font weight and spacing, the bezel positions line up with the markers, and the watch holds pressure at its rated depth, you have a well-built copy. If any one of those checks fails, the price and the box do not matter.

Tools and reference data to gather first

  • The spec sheet for reference IW329120: case diameter, thickness, lug-to-lug, lug width, crystal type, and water-resistance rating. Take these numbers from the manufacturer's product page, never from a seller listing.
  • Digital calipers accurate to 0.01 mm.
  • A 10x loupe and a bright diffused light.
  • High-resolution photos of the genuine watch from the front, side, caseback, and clasp.
  • A timegrapher, plus access to a watchmaker who owns a pressure tester.

Step-by-step inspection

  1. Measure the case at the 3 and 9 o'clock points and compare the reading with the reference spec. A difference past about 0.3 mm changes how the watch sits and points to a generic case.
  2. Measure case thickness at the center of the caseback and lug-to-lug across the outer lug edges. Copies often gain 0.5 mm to 1 mm in height because the movement sits on a thicker spacer.
  3. Remove the strap and measure the lug opening. A 20 mm or 21 mm gap that misses the reference figure makes every replacement strap fit badly.
  4. Study the case finishing through the loupe. Look for a clean border between brushed and polished zones, consistent brushing direction, and defined chamfers along the lugs.
  5. Turn the bezel through a full rotation and count the clicks. Confirm the 12 o'clock marker or pip lines up with the dial index and that the action has no back play.
  6. Inspect the dial print at 10x. Check the font, the space between text lines, the logo size, and whether every applied index sits parallel to its printed track.
  7. Check the hands for length, shape, and finish. The minute hand should reach the minute track and the seconds hand should sweep without stutter.
  8. Examine the date window. Look at its position, the bevel of the aperture, and the font on the date wheel, since the wrong numeral shape is the most common giveaway.
  9. Tilt the crystal under a lamp and note the color of the anti-reflective coating. Compare it with your reference photos, since coating tint and internal reflection are hard to fake.
  10. Open the caseback with the correct tool and identify the movement. Note the caliber stamping, rotor engraving, jewel count, and surface finish. A decorative plate glued over a generic automatic is a downgrade, not a detail.
  11. Read the caseback engraving with the loupe. Judge the depth, font weight, letter spacing, the format of the reference and serial numbers, and the placement of the Swiss Made marking.
  12. Fit the bracelet or strap and check the end links. There should be no gap at the lugs, and the clasp markings, link construction, and rubber edges should match the original design.
  13. Pressure test the watch. Ask for a dry test at 3 bar first, then a test at the rated depth with a 20 percent margin. A screw-down crown and seated gaskets should pass; a failure means no swimming.
  14. Run the movement on a timegrapher in three positions and record rate, amplitude, and beat error before you commit to the purchase.

Red flags to walk away from

  • Photos that never show a straight-on dial shot, a caseback shot, or macro of the print.
  • No pressure-test result offered, or a claim of water resistance with no test equipment involved.
  • Lume that dims within a few minutes under a lamp.
  • Weight that feels light for a steel case of the same size.
  • Movement photos that hide the balance wheel or show a rotor that does not match the reference caliber.

After you buy

Have a watchmaker reseat the gaskets, retest the case, and confirm the crown threads are clean. Torque the caseback to spec, keep the bracelet screws tight, and log the timegrapher numbers so you can spot drift later. A quick service at the start costs less than a flooded movement later.