Short Answer

A replica IW329108 is a copy of the IWC Big Pilot's Watch 43, a time-only pilot watch with a 43 mm case and a 60-hour automatic movement. A good replica matches the case size, dial layout, crown action, and 4 Hz beat rate. A weak one runs thick, prints heavy lettering, and hides a slower movement under a decorated plate. Run the checks below in order and you will know which one sits on the table.

Prerequisites

  • Reference photos of the genuine IW329108 from the maker's catalog
  • Digital calipers
  • 10x loupe
  • Bright desk lamp and a dark cloth
  • A reference clock and 48 hours of test time

Step 1: Measure the Case

  1. Close the calipers across the case at 3 and 9 o'clock, crown excluded. The reading should be 43.0 mm, within about 0.3 mm.
  2. Measure front to back through the center and compare the number with the published spec. More than 1 mm of extra thickness points to a spacer ring and a smaller movement.
  3. Measure lug to lug and the gap between the lugs. The strap should fill the lugs edge to edge with no daylight around the spring bars.

Step 2: Read the Dial Under a Loupe

  1. Hold the watch under the lamp at an angle and inspect the brand name and the Schaffhausen line. Lettering should be crisp and evenly spaced, with no ink halo at the edges.
  2. Compare the numerals with a reference photo. The triangle at 12 and the surrounding indices should sit on one line, and the minute track should run without breaks.
  3. Confirm the layout is time-only. The genuine reference has no date. A date window in the listing means the watch is a copy of a different model.
  4. Check the hands. Lume should sit flush inside the frame, and the hour and minute hands should be level and parallel to the dial.

Step 3: Test the Crown and Time Setting

  1. Unscrew the crown and feel the threads. They should engage without grit or wobble.
  2. Wind 25 turns. Resistance should build and stay even. A crown that spins free at the end of winding has a slipping click.
  3. Set the hands to 12 and look straight on. Hour and minute should line up on the marker, and the seconds hand should stop on the index.

Step 4: Time the Movement

  1. Wind the watch fully and set it down for 24 hours. Compare it with a reference clock and write down the gain or loss.
  2. Check the beat rate with a timegrapher or a phone app. A clone of the 82100 caliber runs at 28,800 vph. A 21,600 vph reading is common on cheaper builds and should lower the price you accept.
  3. Let it run from a full wind and note when it stops. Forty hours is the floor for a serious build; the genuine spec is 60.

Step 5: Check Strap, Crystal, and Seals

  1. Twist the strap at the buckle end. Stitching should pass through the leather, not sit on a glued seam.
  2. Breathe on the crystal and watch how the fog clears. Sapphire clears fast; mineral glass holds haze longer and scratches with a fingernail test.
  3. Do not swim with it. Depth markings on a replica are a claim, not a test, and the caseback gasket is the first part to fail.

What the Results Mean

A replica that passes all five checks sits at the top of the replica market and is worth top money. One that fails thickness and beat rate is a $100 watch with a good photo set. Ask the seller for caliper photos and a timegrapher screenshot before you pay, and treat a refusal as a failed check.