A fake IW371631 is a counterfeit version of an IWC Portugieser chronograph from the 3716 reference block, and the quickest way to expose one is to compare the movement, the dial printing under magnification, and the caseback engraving against IWC's own reference data. Genuine watches show evenly spaced, sharply cut text, a correctly signed movement, and serial numbers that line up with the paperwork. Most fakes fail at least one of those three checks.
What IW371631 actually refers to
The IW3716xx range belongs to the Portugieser Chronograph family, a line known for a clean dial, two sub-dials at 12 and 6, and a slim bezel. Because the reference block covers several dial colors, strap options, and regional or boutique editions, the last three digits matter. Before judging any watch, pull the exact reference from IWC's catalog and confirm the dial color, case metal, and strap it should have. A seller who cannot match those basics is the first warning sign.
Five checks to run first
- Dial printing. On a genuine dial, lettering is crisp and level, with consistent stroke width. Fakes often show fuzzy edges, uneven spacing between "Schaffhausen" and "Automatic," or a logo that sits slightly off center.
- Sub-dial spacing. The two registers should be symmetrical and evenly inset from the chapter ring. Cheap replicas crowd them or misalign the chronograph hands at zero.
- Hands and markers. Look for flat, mirror-polished edges and a clean bevel. Plated replica hands look cloudy or show peeling at the tips.
- Caseback engraving. Depth and consistency matter. Laser-etched fakes look shallow or gray rather than cut.
- Strap and buckle. Stitching density and buckle engraving are easy to fake badly and hard to fake well.
Movement and the tell most fakes cannot hide
A chronograph movement is expensive to copy. Look at the balance, the finishing on the bridges, and how the chronograph starts, stops, and resets. A genuine movement snaps back to zero instantly and holds alignment. Many counterfeits use a modified third-party chronograph module, so the pushers feel mushy and the reset hand lands a fraction off. If you can see the movement, check for signed rotor engraving and perlage or Geneva stripes applied evenly rather than printed on a plate.
Box, papers and serial consistency
Counterfeit sets often reuse the same serial across many units. Compare the number on the caseback with the warranty card, the booklet, and any service records. Genuine paperwork uses consistent typography and matches the reference exactly. A box that smells of fresh glue or a card printed on the wrong stock is a strong indicator that the watch is a fake IW371631 rather than an authentic piece.
How premium replicas differ from cheap counterfeits
There is a wide gap between a low-cost counterfeit and a high-grade replica. Better replicas invest in case finishing, sapphire crystal clarity, and dial printing, so they pass a casual glance. They still fail a hands-on inspection of the movement, the crown action, and the weight of the case in hand. Knowing that difference helps you evaluate any watch honestly, whether you are buying a replica on purpose or trying to avoid a counterfeit sold as genuine.
Before you pay
Ask for sharp macro photos of the dial, caseback, crown, and clasp, plus a short video of the chronograph running. Compare everything with the official reference listing. If details do not match, or the price is far below the going market range for that reference, treat the watch as a fake IW371631 and walk away.