Short answer
A "replica IW371770" is a counterfeit copy of the IWC Portofino Chronograph, a stainless steel automatic chronograph that sells new for several thousand dollars. The copy is not a cheaper version of the same watch. It is a different watch wearing the same dial text, usually built around a cloned or substituted movement, with no relationship to IWC, no parts support, and no lawful way into the United States.
What the reference number refers to
IW371770 sits in IWC's Portofino Chronograph family: a polished steel case in the 42 mm range, sapphire crystal, a two-register chronograph layout, and IWC's caliber 79320, a modified Valjoux 7750 running at 28,800 vibrations per hour. IWC publishes the reference specs on its own site, and that page is what you check a listing against, not a seller's photos.
What the copy usually contains
- An Asian 7750 clone, a cheaper 21,600 vph automatic, or in the budget tier, quartz.
- Mineral glass or low-grade sapphire, often without double-sided anti-reflective coating.
- Printed or badly applied indices instead of faceted applied markers.
- Hollow end links, stamped clasps, and hardware that sheds its finish within months.
- Water resistance that was never tested and should be treated as zero.
Where they give themselves away
Dial printing is the fastest tell. Font weight, letter spacing, and the alignment of the text above and below the subdials are hard to fake at this price. Then the chronograph: start it, reset it, and watch where the hand lands. A genuine 79320 snaps back to zero every time. Look at the date wheel font and the bevel around the date window. Check the caseback engraving under a loupe; reference and serial numbers on real IWC cases are cut clean and deep. Run your thumb over the crown threads and feel the winding. On a copy, all of it feels a little coarse.
One caveat: a timegrapher reading is not proof on its own. The Asian 7750 clone also beats at 4 Hz, so the dial, case, and movement need to be judged together by someone who knows IWC.
The US legal reality
Counterfeit goods are illegal to import, full stop. There is no personal-use exemption for counterfeits, and Customs seizes and destroys shipments when it finds them. Selling or trafficking carries federal criminal exposure under 18 U.S.C. § 2320, plus civil liability to the trademark holder. Buying one inside the US does not turn it into a lawful item you can resell, and marketplaces pull listings and suspend accounts when they catch them.
The ownership math
Most copies run a few hundred dollars. What you get for that: no service network, no parts, a watchmaker who may refuse to open it, and resale value near zero. A genuine 79320 is a known quantity that any competent watchmaker can service, and the watch holds most of its value. If a deal looks like a Portofino at a tenth of the price, it is a copy and the seller knows it. If you already own a watch you suspect, have a watchmaker photograph the movement and check the serial with IWC before spending anything on it.
Bottom line
The same playbook applies here as with the Rolex references: verify the reference number against the maker's own specs, get the movement inspected, and treat any "personal use is fine" claim as false. Buy the real thing or buy something honest. There is no third option that ends well.