Short answer
A fake IW323773 gives itself away in four places: the caseback engraving, the case dimensions, the dial printing, and the movement finish. Check those first. Genuine IWC watches in the 3237 reference family have deep, crisp engraving with even letter spacing, dimensions that match the published spec to within a fraction of a millimeter, and movement finishing that a copy factory does not reproduce at the same level.
Prepare these tools
- A 10x jeweler's loupe.
- Digital calipers that read to 0.01 mm.
- A kitchen scale accurate to 1 gram.
- Bright, diffused light and a plain background.
- The official spec sheet for the reference.
- A watchmaker who can open the case for you.
Step-by-step checks
- Confirm the reference number exists in the manufacturer's own records before you inspect the watch, so you know which dial, case size, and movement the seller claims to be selling.
- Measure the case diameter with calipers across the bezel on the 3 to 9 o'clock line, then compare the reading with the published diameter for that reference.
- Measure the thickness from the top of the crystal to the center of the caseback, because copies often run thicker than the original.
- Weigh the watch head on its own, without the strap or bracelet.
- Put the 10x loupe on the dial text and compare stroke weight, letter spacing, and alignment of the brand name against reference photos.
- Inspect the date window for a clean aperture edge, then cycle the date through several numbers to see whether each numeral sits centered.
- Examine the crown and pushers under the loupe for engraving quality, sharp edges, and how far they protrude from the case.
- Turn the watch over and read the caseback engraving with the loupe, checking depth, font, and consistency of both the reference and serial numbers.
- Match the serial number format against the production era of the reference, since a serial from the wrong period is a common error in copies.
- Ask the seller for service paperwork or an extract from the maker's records, and treat a refusal as a reason to walk away.
- If the case has a display back, examine the rotor engraving, the finishing on the bridges, and the color and shape of the screws.
- Look at the crystal at an angle under a light. Genuine anti-reflective coating gives a faint, even tint. A cheap coating looks like a heavy blue film or is missing on the inner surface.
- Hand the watch to a watchmaker and have the movement inspected and its caliber identified.
Red flags that settle it fast
- Text that is too bold, too thin, or spaced unevenly.
- A crown that wobbles or grinds when you wind it.
- Lume that glows hard for a few minutes and then dies.
- Bracelet end links that rattle against the case.
- Sharp, unfinished edges on the lugs and clasp.
- A caseback with shallow engraving that feels smooth to a fingernail.
- A watch that feels light for its size and case material.
- A seller who refuses an inspection or a return window.
Where a guide stops
Photos and measurements take you far, not all the way. High-end copies use movements built to look correct at a glance, and some are assembled with genuine parts. Only an inspection inside the case gives a firm answer. Budget for that check before you pay, and keep the sale conditional on the result. If the price looks too low for the reference, the watch is the problem, not your luck.