Quick answer
IW371775 is an IWC reference inside the Portugieser Chronograph family. Fakes of this reference appear in three grades: quartz or low-beat automatics, copies built on an Asian Valjoux 7750, and top-grade copies with a decorated clone movement. Judge any copy on four points: subdial function, case thickness, dial print quality, and caseback engraving.
IWC has released many Portugieser Chronograph variants in the 3717xx block. The exact dial and case combination sold as IW371775 is not listed in most public catalogues. Confirm the reference with the seller before you compare details, and compare against photos of the same dial variant.
What the genuine watch does
The Portugieser Chronograph is a 41 mm steel watch, about 13 mm thick, rated to 3 bar. The dial has two subdials stacked vertically: chronograph minutes at 12 and running seconds at 6. The date sits at 3. The movement is the in-house calibre 69355, a column-wheel chronograph with a 46-hour power reserve and a 28,800 vph beat rate. Sapphire covers both the dial and the display back.
Subdial function is the first test
- Running seconds at 6 must sweep in small steps. A hand that jumps once per second is quartz.
- The 12 o'clock subdial counts chronograph minutes, not hours. Start the chrono and watch which hand moves.
- Reset must snap both chrono hands to zero at the same instant. A lazy reset points to a cheap module.
A stock Valjoux 7750 has running seconds at 9. Copy makers must re-gear the motion works to move seconds to 6. That extra gear train is where mid-grade fakes show play, stutter, or a stopped subdial.
Measure the case
Use calipers, not photos. Genuine thickness is near 13 mm including the crystal. Many 7750-based copies measure 14.5 mm or more and sit tall on the wrist. A 41 mm diameter is standard across the line, so width rarely exposes a fake. Thickness and lug shape do.
Dial and print
- Applied numerals are thin, polished, and sit flat. Fakes use thicker numerals with rounded edges.
- The minute track sits on the outer edge with even spacing. Check the gap at 12.
- Print on the date wheel matches the dial font. A fat or serif number is a tell.
- Hands are polished and flat, with a clean center hole.
Caseback and engraving
Genuine engraving is crisp, with sharp inner corners on the letters and a consistent depth. Laser-etched fakes look shallow and slightly fuzzy under a loupe. The rotor on the 69355 has a specific finish and text layout. Compare the text position against a reference photo of the same movement, since copy makers often copy one movement photo across several references.
Buying checklist
- Ask for a video of the chronograph start, stop, and reset.
- Ask for caliper readings of diameter and thickness.
- Ask for a macro photo of the dial print and the date window.
- Ask for a photo of the movement through the caseback.
- Pressure test the watch before swimming. No replica ships with a valid water resistance rating.
Price tracks grade. A copy far below the going rate for top-tier work is a lower tier with better photos.