Short answer
A fake IW323734 almost always fails on three points: the caseback engraving, the movement visible through the display back, and the crown action. Genuine IWC casebacks carry crisp, shallow laser engraving with consistent letter spacing and a reference number that matches the paperwork. Replicas use deeper stamped or etched lettering with soft edges. If the seller cannot show a clear macro photo of the caseback and the movement, treat the watch as fake and walk away.
Before you start
- A 10x loupe or a phone camera with macro mode
- Digital calipers for case diameter and thickness
- A kitchen scale accurate to 0.1 g
- Bright, angled light and a clean microfiber cloth
How to check the watch
- Ask the seller for the full reference number as engraved on the caseback, not as printed in the listing. The two must match exactly, digit for digit.
- Compare case diameter and thickness against the published specification with calipers. Replica cases run thick, often by 0.5 mm to 1.5 mm, because the clone movement sits deeper.
- Weigh the watch head on its own. A genuine piece lands within a gram or two of the catalog figure; plated brass or thin steel cases come in visibly light.
- Inspect the caseback lettering under the loupe. Genuine engraving sits flush with even depth, and the reference and serial numbers use the same font weight as the surrounding text.
- Look at the dial printing at an angle. Genuine appliqués and text sit flat with sharp edges; replicas show raised ink, fuzzy serifs, and misaligned markers.
- Check the hands under magnification. Genuine hands have beveled, polished edges and no tool marks at the center cap.
- Wind and set the crown through a full cycle. Genuine crown threads engage smoothly in half a turn, with firm clicks at each position and no lateral wobble.
- Examine the movement through the display back. Look for perlage or Geneva stripes with even spacing, polished screw heads, and a correctly spelled rotor engraving.
- Time the watch over 24 hours against a reference clock. A genuine movement holds within a few seconds a day; a cheap clone drifts far more and often stutters when the seconds hand starts.
- Match the serial number against the warranty card, the caseback, and the movement bridge. All three should agree.
Red flags
- Stock photos only, or photos that blur the caseback and movement
- A price far below the going rate for the reference, with pressure to buy fast
- No box, no papers, and a story about a lost warranty card
- Seller refuses a video call or an in-person inspection
- Caseback text with a font mismatch, uneven spacing, or a missing hyphen
- Serial number that repeats across multiple listings from the same seller
What to request in writing
Ask for a macro photo of the caseback, a photo of the movement with the rotor turned, a short video of the crown being set, and a copy of the warranty card showing the dealer stamp. Get the return window in writing before you pay. A seller with a genuine watch will supply all four without argument; a seller with a fake will stall, crop the images, or push you to a wire transfer.