Short answer
The IW371629 is a stainless steel IWC Portugieser Chronograph, and most fakes fail on three things: the movement behind the sapphire case back, the crispness of the dial printing, and the depth and font of the case back engraving. A counterfeit can copy the silhouette from across a table, but it cannot copy the calibre, the column wheel feel of the pushers, or the finishing of a real IWC case.
What the genuine watch is
The IW371629 sits in the Portugieser Chronograph family, a line IWC has produced in several dial and strap variations under the 3716 reference block. The genuine article uses an in-house automatic chronograph calibre, a 41 mm steel case, a domed sapphire crystal, and a display back. Confirm the exact dial color, strap option, and calibre number against IWC's own reference data before you judge any single watch, because specifications shifted across production years.
How to check an IW371629 for authenticity
- Ask the seller for a clear photo of the case back and read the reference number. It should read IW371629 with the IW prefix, and the engraving should sit deep in the metal with sharp edges.
- Measure the case if you can handle the watch. A 41 mm diameter and roughly 13 mm thickness match the genuine case, while most copies run thicker and heavier in the hand.
- Study the dial text under a loupe. The IWC SCHAFFHAUSEN signature and the subdial markings should be level, thin, and free of the fuzzy edges that come from pad printing on a copy.
- Compare the subdial layout and hand finish to photos of the real reference. Both chronograph registers should sit on the same horizontal line at 12 and 6, with the same azurage texture inside.
- Turn the watch over and look through the display back. You want to see an IWC signed rotor, Geneva stripes, and a calibre designation stamped on the movement bridge, not a blank plate or a generic chronograph module.
- Press each pusher. A genuine column wheel chronograph starts and stops with a light, precise click, while a fake built on a modular movement feels soft or gritty.
- Check the crown action and the date change if the reference has a date. The crown should screw down with smooth threads and the date should jump clean at midnight.
- Inspect the strap, buckle, and clasp engraving. Genuine hardware carries the same crisp lettering as the case, and the buckle tang or deployant should show no casting marks.
- Verify the box, warranty card, and service papers against the serial number on the case back. Ask whether the watch is eligible for registration in IWC's owner portal, since a serial that will not register is a strong warning sign.
- Take the watch to an independent watchmaker and have the case back opened. A timing machine reading plus a look at the movement finish settles the question in minutes.
Common red flags
- Case back engraving that is shallow, laser faded, or set in the wrong font.
- Dial text that is bold, uneven, or crowded against the subdials.
- A closed case back on a reference that should have a display back.
- Pushers that screw down, stick, or rattle when you shake the watch.
- A price far below the going rate for a used Portugieser Chronograph.
- A seller who refuses to open the case back or meet at a watchmaker.
Before you buy
Buy from an authorized dealer or a pre-owned seller with a written return policy, and treat any IW371629 sold without papers as a watch that needs inspection first. If the price looks too good, assume the watch needs opening before money changes hands.