Quick answer
A replica IW371689 is a copy of the IWC Portugieser Chronograph: a 40.9 mm steel case, a two-register dial with the chronograph minutes at 12 and running seconds at 6, leaf-shaped hands, and a display caseback. Good copies match the case profile and dial printing. Weak copies miss the subdial spacing, use wrong hand shapes, and run 1 to 2 mm too thick. Inspect four things before you pay: case thickness, subdial behavior, print sharpness, and the movement you can see through the back.
Reference points to compare against
Measure the watch you are offered against the published specs of the genuine reference. Bring calipers or ask the seller for a photo on a ruler.
- Case diameter: about 40.9 mm
- Case thickness: about 13.1 mm
- Lug width: 20 mm
- Water resistance on the original: 3 bar
- Chronograph layout: 30-minute counter at 12, running seconds at 6
- Power reserve: roughly 46 hours on the genuine caliber
How to inspect a replica IW371689
- Measure the case thickness with calipers at the center of the caseback.
- Reject the watch if the reading passes 14 mm, since that points to a thick chronograph module stacked on a base movement.
- Start the chronograph and watch the counter at 12 for a full minute.
- Confirm the counter jumps once per minute and completes one revolution in 30 minutes.
- Stop the chronograph and reset it, then check that both hands snap back to zero at the same moment.
- Look at the dial print under a loupe at the 12 and 6 numerals.
- Compare the leaf hands to a reference photo, focusing on the taper and the curve at the tip.
- Turn the watch over and read the rotor engraving and the balance area through the caseback.
- Check the crown for correct engraving depth and a firm, click-free winding feel.
- Flex the strap at the lugs and look for uneven stitching or a hollow feel.
Movement: what is actually inside
The genuine reference uses an in-house chronograph caliber with a column wheel and a vertical clutch. No replica at any price reproduces that architecture. Most copies run a modified Valjoux 7750 derivative, which is reliable and serviceable but visually different from the original through the back. Expect a decorated rotor and perlage on the bridges. Treat any claim of a true column-wheel clone as a marketing line until you see the movement photographed without the caseback installed.
Dial details that separate price tiers
The dial is where most of the money goes. On a strong copy the minute track is crisp and evenly spaced, the applied numerals sit flat against the surface, and the subdial rings are recessed with a clean step. On a cheap copy the track looks soft, the numerals catch light at an angle, and the subdial rings are printed rather than stepped. Ask for a straight-on macro photo of the dial in daylight, not a studio render.
Price bands and red flags
Entry copies sit in the low hundreds of dollars and show it in the thickness and the print. Mid-tier copies fix the case profile and the dial but keep the base movement. Top-tier copies add a closer hand set, a better crystal, and a properly shaped caseback. Walk away from any listing that uses official brand photography, refuses a timestamped photo, or quotes a delivery time measured in days from a warehouse that does not exist.