Short answer
A fake IW545170 fails first on case geometry, dial printing, and movement finish. Genuine IWC Portuguese references are machined to tight tolerances, and replicas copy the look from photos, so the numbers rarely match. Work in a fixed order: case profile, dial and hands, crown, caseback, movement, then paperwork. One clean failure ends the inspection. You do not need three strikes.
Prerequisites
- Digital calipers with 0.01 mm resolution.
- 10x jeweler's loupe.
- Bright, diffuse light and a lint-free cloth.
- Caseback opener matched to the caseback type, or a watchmaker who has one.
- IWC's published specification sheet for the reference, printed or on screen.
Step-by-step comparison
- Look up the official case diameter and thickness for the IW545170 on IWC's reference page and write both numbers down.
- Measure the case diameter and thickness with calipers at three points and compare each reading to the official figure. A replica that is 0.5 mm thick or more beyond spec is a rejection.
- Run a loupe along the case flank and the lug edges, checking for machining marks, rounded transitions, and polish that bleeds onto brushed surfaces.
- Examine the dial print at 10x, checking letter spacing, stroke weight, and whether the printing sits flat or shows a raised edge.
- Check the small seconds sub-dial position against the center line, then confirm the sub-dial ring finish matches the main dial.
- Study the hands under the loupe for burrs, uneven polishing, and paint that stops short of the hand edge.
- Inspect the crown engraving and the crown tube fit, then confirm the crown winds with defined, even clicks.
- Turn the watch over and read the caseback engraving: reference number, serial, and hallmarks should be crisp, correctly spaced, and consistent with each other.
- Open the caseback and inspect the movement through the loupe for perlage or Geneva stripes that stop at edges, rough bevels, and engraved text cut with a laser instead of a die.
- Match the movement caliber and the rotor or bridge markings to the caliber IWC lists for that reference.
- Compare the warranty card, booklet, and box printing to a known genuine set, focusing on font, paper stock, and serial placement.
- Take the watch to an independent watchmaker for a timed rate check and a movement identification before any money changes hands.
Common tells on replicas
- Case thickness that runs heavy because the replica case houses a thicker third-party movement.
- Dial print that looks correct at arm's length and fuzzy at 10x.
- Polished bevels that reflect light in a wide band instead of a thin line.
- Caseback engraving that is shallow, or a serial that repeats across listings.
- Movement decoration applied over a stock caliber, visible at the plate edges.
- Paperwork with the wrong paper weight or a serial that does not match the case.
When to walk away
Stop the inspection if the seller refuses a caseback opening, blocks an independent watchmaker's review, or supplies photos only. A genuine IW545170 will survive every check on this list without excuses. Price is not evidence either way, so judge the watch, not the story attached to it.