Replica IW371766: the short answer
A replica IW371766 succeeds or fails on four checks. Case size and thickness come first. Dial layout and printing come second. Chronograph action comes third. Movement type behind the caseback comes last. The genuine Portugieser Chronograph measures 41 mm across and runs IWC calibre 69355, a column-wheel design with a 46-hour reserve. Many copies use a Valjoux 7750 base, which adds thickness and shifts subdial geometry. Settle those four points before you discuss hand finishing or strap quality.
Prerequisites
- Digital calipers with 0.1 mm resolution
- Reference photos of the genuine 41 mm Portugieser Chronograph, front, side and caseback
- Seller QC images shot in daylight, plus a short video of the chronograph start, stop and reset
- 10x loupe
- Timegrapher readout if the seller will provide one
Inspection steps
- Measure the case diameter across the bezel at two points. Target 41 mm on both.
- Measure thickness at the caseback rim. The genuine sits near 13 mm. A 7750-based copy often reads 14.5 mm or more.
- Confirm lug width. The genuine takes a 20 mm strap, and the lug curve should match your reference side photo.
- Lay a straight edge along the dial. Subdials belong at 12 and 6 on the vertical axis, with the small seconds at 6.
- Study the dial print under the loupe. Check letter weight, spacing and the finish of the applied numerals.
- Start the chronograph and let it run ten minutes. Then reset. The hands should snap to zero in one motion with no creep.
- Press each pusher. Travel should be short and firm. A gritty or loose pusher points to a cheap 7750 build.
- Set the hands to 12 and check alignment of the chronograph seconds against the minutes hand.
- Turn the watch over and read the caseback engraving depth and the rotor decoration.
- Ask for a 24-hour rate reading. Anything past plus or minus 15 seconds per day needs a service quote.
Red flags
- Flat printed subdials in place of recessed, snailed counters
- Thick or blurred SWISS MADE print at 6
- Movement stamped with a calibre number the seller cannot explain
- Sapphire with a heavy blue tint at the edge
- Caseback screws that sit proud of the rim
- Strap stitching that wanders off the edge line
What to expect after purchase
Treat a replica IW371766 as a mechanical watch with no factory backing. Water resistance claims on copies rarely hold, so keep it away from taps, pools and steam. A 7750 base needs a service interval of roughly three to five years under daily wear. Budget for that cost at the point of sale, not after the first stall. Legality of buying and importing replicas varies by country, and a replica is not a genuine IWC product.