Quick answer
A fake IW5105 fails in three places: the dial print, the seconds hand, and the caseback engraving. IWC finishing is tight, and the reference is low volume, so counterfeiters do not tool a dedicated case for it. They take a stock Portugieser style case, print a dial, and label the listing IW5105. If you can see the movement and read the engraving under magnification, the call takes about five minutes.
What the IW5105 label covers
IWC uses long reference strings for the Portugieser family, and sellers shorten them for search. The shortened form drops the middle digits and leaves a four or five digit number that buyers pass around in forums. That is why a search for the reference returns watches with different dial colours and case metals under one label.
Two consequences follow. First, official product photos matter more than forum photos, because forum photos often show a different variant. Second, a genuine example should carry a full reference on the paperwork and on the caseback, not the short form used in listings.
Prerequisites
- A 10x loupe or a phone macro lens
- Digital calipers
- A strong raking light, such as a phone torch held at a low angle
- Official IWC product photos of the exact variant, at known scale
Inspection sequence
Work through the steps in order and stop at the first clear failure.
- Set the watch to a known time, then watch the seconds hand for 60 seconds against a reference clock.
- Measure the case diameter and lug width with calipers and write both numbers down.
- Hold the light at a low angle across the dial and examine the printing through the loupe.
- Flip the watch and read the caseback engraving under the same light.
- Remove the strap and inspect the lug holes, spring bars, and inner lug finishing.
- Ask for the movement to be shown, or have a watchmaker open the caseback.
Dial printing and subdial spacing
Real IWC dials use crisp, thin printing with sharp terminals on every letter. Fakes show bleed at the edge of the text, uneven stroke weight, and numerals that sit a fraction off centre. Check the gap between the subdial and the outer track. A printed dial from a generic supplier will not match the spacing in the official photo, and the mismatch grows when you overlay the two images.
Movement behaviour and power reserve
Wind the watch fully, note the time, and set it down. A genuine IWC movement in this family runs for several days on a full wind and keeps time within a few seconds a day. A quartz fake ticks once per second. A low grade clone beats at a lower rate and shows a stutter when you slow the sweep down on video. Check the power reserve against the stated figure. If a listing claims a long reserve and the watch stops overnight, the claim is invented.
Case, lugs, and polishing
Run a fingernail along the case flank where brushed surfaces meet polished ones. Real cases have a clean, straight transition. Fakes show a soft, rounded edge from a buffing wheel, and the brushed grain wanders. Compare the lug curvature with the official photo. Generic cases use a shallower curve that sits differently on the wrist.
Caseback engraving and serials
Engraving is the hardest detail to copy at low cost. Real markings are cut deep with uniform depth and sharp internal corners. Fakes are laser etched, so they look shallow and grey, and the letters carry a slight halo. Read the reference and serial and confirm they match the certificate. Serials on fakes repeat across batches, so a quick image search for the number ends the discussion.
Strap, buckle, and box
Check stitch density and spacing on the strap. Real straps use even stitching with consistent thread thickness. Check the buckle tang for sharp edges and correct thickness. Boxes and papers are easy to fake, so treat them as supporting evidence only, never as proof.
Red flags that end the inspection
- Seller refuses a caseback photo or an in person inspection
- Serial number appears on more than one watch in search results
- Reference on the papers differs from the caseback
- Price sits far below the market range for the variant
- Photos are stock images or show a different dial colour than the listing text
Verification before money changes hands
- Pull the exact reference from the official IWC site and save the product images.
- Request the service history and the original certificate.
- Book a watchmaker to open the case and photograph the movement.
- Ask the brand or an authorised service centre to confirm the serial.
- Pay through a method that allows a chargeback if the watch is not as described.