A fake IW371619 usually fails within a minute of handling. The reference belongs to the current Portugieser Chronograph family: 41.0 mm steel case, roughly 13 mm thick, sapphire display back, and the in-house caliber 69355 column-wheel chronograph. Real examples have no luminous paint anywhere, print the dial markings with sharp edges, and show Geneva stripes plus a column wheel through the back. Check those four points first. If any one is off, the watch is not genuine and no other detail matters.
What a genuine IW371619 should show
- Case diameter 41.0 mm, thickness close to 13.0 mm, lug width 20 mm.
- Vertical subdial layout: 30-minute counter at 12, small seconds at 6, no date window.
- Applied numerals at 12 and 6, slim leaf hands, no lume on hands or markers.
- Caliber 69355 behind sapphire, 4 Hz, about 46 hours of power reserve, column wheel and vertical clutch.
- Water resistance rated 3 bar, engraved with the reference and a serial between the lugs or on the caseback rim.
How to check a watch, step by step
- Measure the case with calipers and confirm 41.0 mm across the bezel and about 13.0 mm through the caseband.
- Weigh the watch on a digital scale and compare the figure with a known genuine example on the same strap or bracelet.
- Turn the dial to a lamp and inspect the printed track, the IWC signature, and the Schaffhausen text at 3x magnification.
- Look for lume by charging the hands and numerals with a phone torch in a dark room, since a glow means a fake dial.
- Start the chronograph and watch the 30-minute hand at 12 snap back to zero with a firm, single push of the lower pusher.
- Flip the watch over and confirm a sapphire crystal with an anti-reflective coating, then study the movement finishing under a loupe.
- Find the column wheel near the balance and check that the bridges carry clean Geneva stripes and crisp engraved text.
- Read the caseback engraving for the reference number, the serial, and the Probus Scafusia wording, then compare the fonts with the reference listing on IWC's own site.
- Inspect the crown and pushers for signed, sharply cut edges and a flush fit against the caseband.
- Check the strap stitching and buckle markings, or the bracelet end links and clasp engraving, for the same font and finish quality as the case.
Where replicas fail most
Thickness is the first giveaway. Most fakes built around a stock chronograph movement run 1 to 2 mm thicker than the real watch, and the caseback sits proud of the wrist. Dial print is the second: replica text looks slightly bold, the minute track dots merge, and the subdial rings sit at the wrong distance from center. The third is the movement. A fake will show a decorated rotor over an undecorated base plate, no column wheel, or a solid caseback where the reference should have sapphire.
Hands, crystal, and case details
Genuine leaf hands are thin at the tip and polished on all faces, with no paint fill. The sapphire carries anti-reflective coating on both sides, so the dial stays legible from an angle without a blue or purple cast. Case finishing should be consistent: polished surfaces free of swirls from a buffing wheel, crisp edges where the lugs meet the caseband, and a bezel that sits perfectly concentric with the dial.
Paperwork and price checks
Ask for the warranty card, the booklet, and the original invoice. Compare the serial on the card with the serial engraved on the watch, and confirm the reference matches the dial and bracelet configuration. Price is a reliable filter: a steel Portugieser Chronograph trades well above the low thousands, so an offer at a few hundred dollars is a replica regardless of the story attached. A seller who cannot show a movement photo through the display back is worth walking away from.