Short answer
A fake IW371778 earns its price on four things: case proportions, dial print and finish, subdial placement, and what sits behind the caseback. Nothing else moves the needle much. The IW371778 belongs to the Portugieser chronograph family, so the tells are the classic Portugieser tells. A dial that reads flat under daylight. Subdials spaced a hair too close to the center. A case that sits two millimeters too tall and slides around under a shirt cuff. Get those right and the watch passes on the wrist. Get them wrong and no amount of box-and-papers dressing will save it.
First, confirm the reference
IWC reference codes run long, and the last digits often encode dial color, strap, or market. Before you compare anything, pin down what the code actually denotes. Pull the specs from IWC or ask an authorized dealer, then build your checklist from that. A replica built off the wrong reference will fail on details that have nothing to do with build quality. Boutique and regional codes also drift over time, so the same number can mean slightly different things depending on the year.
Case and proportions
The Portugieser chronograph lives in the 40 to 41mm range with a slim profile, roughly 13mm or a touch under. That thinness is the hard part for any replica maker. A chronograph module stacked on a generic movement adds height, and the extra millimeter shows up immediately in profile photos and in how the watch sits on the wrist.
- Measure the thickness yourself with calipers. Published numbers and real numbers rarely agree.
- Look at the lug curve. Genuine lugs taper and curve down; sloppy replicas leave them straight and sharp.
- Check the finish split. Polished flanks, brushed lugs, crisp bevels where the two meet. A blurry transition means corners were cut.
- Look at the crown and pushers. They should sit flush, with no gap and no wobble.
Dial and hands
This is where most buyers get burned, because dials photograph well and lie in person. Under direct light, a good dial has depth. The lacquer or sunburst should shift as you rotate the watch. Flat, plasticky color is the single most common flaw I see.
- Printing: the brand text should be sharp and raised, not fuzzy or gray at the edges.
- Applied numerals and markers: even height, no glue visible at the base, no misalignment at 12.
- Subdials: correct spacing from the center, correct snailing or finish, hands that sit level with the dial.
- Leaf hands: the shape should taper cleanly with no stubby tips and no sloppy lume fill.
The movement question
Open the caseback, literally or with photos. Many Portugieser chronographs ship with an exhibition back, so the movement is on display and the finish has to hold up. Chinese clones of the Valjoux 7750 family are the usual base, and they work, but they add thickness and they often rearrange which subdial does what. Check that the running seconds sits where the genuine puts it. Check that the chronograph resets to zero cleanly and that the pushers feel firm rather than mushy. A cheap movement with a decorated rotor is still a cheap movement.
Strap, clasp, and the small stuff
Strap quality is the cheapest thing for a factory to skip and the easiest thing for you to spot. Genuine alligator has visible scale structure and a soft hand. Most replica straps are embossed calf. The clasp engraving should be deep and clean, not laser-etched and shallow. Also check the caseback engraving depth and the serial spacing, since those are common shortcuts.
Before you pay
- Ask for a video, not stills. Rotate the dial toward a window.
- Request caliper shots of thickness and lug width.
- Ask for a close-up of the caseback and the movement.
- Confirm the return policy in writing.
- Compare against dated photos of the genuine reference, not press renders.
A good fake IW371778 is a pleasure to wear. A bad one is a constant reminder. Spend your attention on the case profile and the dial, and the rest tends to sort itself out.