Short answer
IW371629 sits in the IWC Portugieser Chronograph family. A fake IW371629 is a watch built outside IWC that copies the case, dial and strap of that reference. Replica sellers sort these watches into grades: quartz, low-grade automatic, and "1:1" or "super clone." No grade uses a movement from IWC. No grade passes an IWC service check. Buy a genuine one from an authorized dealer or from a seller with service papers and a case number you can verify.
What the genuine reference is
The Portugieser Chronograph 41 line uses a stainless steel case listed at 41 mm across and about 13 mm thick. Water resistance is 3 bar. The dial carries a central chronograph seconds hand, a 30-minute counter at 12 o'clock, and small seconds at 6 o'clock. The glass is sapphire with anti-reflective coating on both faces.
The movement in current 3716 references is calibre 69355. It is an in-house automatic with a column wheel, a vertical clutch, 28,800 vibrations per hour, and a power reserve near 46 hours. Earlier Portugieser Chronograph references used calibre 79350, a reworked Valjoux 7750.
Public spec sheets confirm the line and the calibre. They do not all list the exact dial, hand and strap combination for reference IW371629. Check that detail against an IWC dealer record or the papers that come with the watch.
How fakes are graded
- Quartz: battery movement, subdials that do not advance, case from a mold. Street price under $100.
- Low-grade automatic: Asian 7750 copy or a Seagull ST19. Pushers feel loose, date font is wrong, rotor noise is loud.
- "1:1" or "super clone": closer case finishing and a clone movement. Price range $400 to $900. Still no IWC parts.
Checks that catch most fakes
- Subdial function. The 30-minute counter must step one minute at a time while the chronograph runs. Painted or frozen subdials are a fake sign.
- Caseback text. Reference, serial and movement numbers are engraved into the metal, not printed on a sticker or a flat pad print.
- Case thickness. A clone 7750 adds height. Measure with calipers. A watch at 15 mm is not a 3716 case.
- Pusher feel. A column wheel chronograph starts with a light, clean click. A cam-actuated clone feels stiff and gritty.
- Dial print. "Schaffhausen" and "Automatic" sit on one line in the genuine layout. Compare letter height and spacing to an IWC photo.
- Hands. Genuine leaf hands are polished on the top face and matte on the side. Plated replica hands look flat under a loupe.
- Bracelet fit. End links on a genuine bracelet meet the lugs with no gap. Replica end links rock under finger pressure.
Movement facts
Calibre 69355 has a column wheel under the chronograph bridge. Where a case back is transparent, that check takes seconds: the column wheel is a round, toothed wheel with vertical posts. Replica movements at this price are cam-actuated and show a flat lever instead. A watchmaker with a timing machine can also read the beat rate. A quartz fake reads no beat error because it is not mechanical.
Price facts
Genuine steel Portugieser Chronograph watches list in the high four figures in US dollars. Replica listings at $300 to $900 sit below the cost of one genuine chronograph service, which runs several hundred dollars. That gap is the clearest single signal.
What no replica has
Serial records. IWC logs each watch by case number, and a service center can match that number to the reference and the build date. A fake has no matching record. Ask for the case number before you pay, then verify it.
Open points
I cannot confirm from public spec sheets which dial, hand and strap variant carries reference IW371629. Treat any listing that shows that number without matching papers as unverified.