Short answer
A replica IW371615 is a 41mm steel chronograph built to look like the IWC Portugieser Chronograph with the blue dial. The better examples get the case profile, dial color, and printed text close enough that the watch reads correctly on the wrist. The consistent weak spot is the movement, because the genuine watch runs IWC's in-house calibre 69355 and no clone has copied that architecture. If you are comparing replicas, check case thickness, subdial function, and date font before anything else.
What the genuine IW371615 is
IWC lists the Portugieser Chronograph ref. IW371615 at 41mm across in stainless steel, 13.1mm thick, with a blue dial, rhodium-plated hands, a date at 3, and sapphire on both sides. Water resistance is 3 bar. Inside sits the calibre 69355, an automatic column-wheel chronograph with a 46-hour power reserve. The layout is two-register: chronograph minutes at 12, small running seconds at 6. Street pricing on a leather strap has hovered around $8,000 in the US, which is exactly why the copy market exists.
How the replicas are built
Most replica IW371615s use a 41mm steel or plated case, a sapphire or mineral crystal, and an Asian 7750 base dressed up with an engraved rotor and bridge plates. A smaller number use a hand-wound Seagull ST19. Both will run, and both will chronograph, but neither behaves like a column wheel. Expect the pusher feel to be softer and the reset snap to be less crisp.
The tells that give a copy away
- Thickness. Genuine is 13.1mm. Many replicas land between 13.8mm and 14.5mm, which changes how the watch sits under a cuff.
- Subdial spacing. If the two registers sit too far apart or too close to the center, the dial proportion is off.
- Subdial function. On the real watch the top register counts chronograph minutes. Copies sometimes wire it as a 24-hour or running-seconds display.
- Date font. The numeral shape and the window bevel are hard to fake at this price point.
- Caseback engraving. Reference numbers, the IWC wordmark, and the movement ring text are usually shallow or slightly wrong in letterform.
- Strap and buckle. Factory straps have a specific grain and stitching pitch. Aftermarket copies rarely match.
Movement limits, stated plainly
A 7750-based copy will be reliable enough to wear, but it is a cam-actuated chronograph with a different winding feel, a different sound, and a different service path. No watchmaker tied to IWC will touch it. Parts come from the gray market, and the movement is not designed to the same tolerances. If the chronograph function matters to you, this is where the gap shows.
Fit, straps, and daily wear
The 41mm case wears larger than the number suggests because the Portugieser has a thin bezel and long lugs. Lug width is 20mm, so straps are easy to source. A replica on a decent leather strap looks the part in a meeting. It will not survive swimming, despite any 3 bar marking on the back, and the plating on cheaper cases will dull within a year.
Legal and practical caveats
In the United States, selling counterfeit goods is illegal, and Customs can seize shipments of goods bearing protected trademarks. Buying for personal use carries lower risk than selling, but the risk is not zero: a seized parcel means lost money and no recourse. There is also no warranty, no parts supply, and no resale value. Treat the money as spent the moment it leaves your account.
A checklist before you commit
- Ask for caliper photos of case thickness, front and side.
- Ask for a video of the chronograph starting, stopping, and resetting.
- Confirm which subdial does what.
- Ask for a clear macro shot of the date window and the dial text.
- Ask for the caseback, inside and out.
- Check whether the seller offers any return window in writing.
Get those six answers and you will know more about the watch in front of you than any listing photo will tell you.