The short answer
Buy the dial and the movement, in that order. On a fake IW371620, almost every visible flaw comes from three places: subdial spacing, the date window, and the extra height a chronograph movement adds to the case. Ask for a live video with the chronograph running and the date changing before you pay, and walk away from any seller who answers with stock photos of the genuine watch. A replica that gets the dial proportions right and holds the case near 13 mm will read as correct on the wrist. One that ships with a perfect box and a 15 mm case never will.
What to look for in a replica IW371620
Dial layout and subdial spacing
The Portugieser Chronograph puts running seconds at 6, a 30 minute counter at 12, and the date at 3. Reps built on a stock 7750 with a transfer plate often drift these positions by a fraction of a millimeter, and the gap between a subdial edge and the nearest applied numeral gives it away. Look at the recess depth of each subdial ring. Genuine has a clear step down into the ring; cheap reps print a flat circle and call it done.
Date window and font
Check position, font weight, and frame. The date should sit centered at 3 with a thin metal frame and numerals that match the dial printing in weight. Ask for photos of the 31st and the 1st so you can see the flip, because a slow or misaligned date wheel is one of the most common faults on a budget chronograph replica.
Case thickness
Genuine sits at roughly 13 mm. Anything past 14 mm is a warning sign, since the added height is a module stacked on top of a 7750. Ask the seller to photograph the case side on next to a ruler, or measure with calipers when the watch arrives and keep the return window open.
Hands, numerals, and printing
Leaf hands with a clean center ridge, applied numerals with sharp edges, and printing that survives a loupe. Soft "IWC" lettering, a flat Schaffhausen script, and numerals that sit high off the dial with visible glue are the three easiest tells on a fake.
Crystal and coating
Box domed sapphire with anti-reflective coating on both faces. Tilt the watch under a lamp: a strong blue or purple flash points to single sided or cheap coating. Genuine has a soft, near invisible AR that mostly disappears at an angle.
Parameter bands worth checking
- Case diameter: 40.8 to 41.2 mm measured across the bezel, crown excluded.
- Case thickness: 13.0 to 13.6 mm is close to spec. Above 14 mm, expect a module.
- Lug width: 20 mm, so aftermarket straps fit without gaps.
- Subdial positions: running seconds at 6, 30 minute counter at 12, date at 3.
- Weight: roughly 75 to 85 g on leather. A very light case points to a hollowed or thin-walled midcase.
- Movement: 7750 base with a chronograph module is the common route. A claimed column wheel clone needs video proof of pusher feel and rotor engraving before you believe it.
- Water resistance: treat any rating as unproven until a watchmaker pressure tests it.
Where buyers get burned
- Listings illustrated with genuine watch photos. Ask for a photo of the actual unit with today's date on a card.
- "Swiss made" claims attached to a Chinese 7750. The movement is what it is; the label is marketing.
- No macro shot of the caseback engraving, reference marks, and serial placement.
- Quartz builds with faux subdials sold as automatic chronographs. Insist on a video of the seconds hand sweeping and the chronograph resetting to zero.
- No written return window. A seller who will not take the watch back on a thickness or date fault is telling you something.
- Strap quality ignored. A stiff, glossy strap makes a good case look cheap, and replacement straps are one of the cheapest upgrades you can make.
FAQ
Is a fake IW371620 worth buying?
It can be, if the dial proportions and case height are right and the chronograph functions cleanly. The Portugieser Chronograph is a dressy, simple design, so the details carry the whole watch. A mid tier replica with a correct dial beats a top tier claim with a thick case.
Will the chronograph actually work?
On a 7750 based replica, yes, and the pusher feel should be firm with a clear start, stop, and reset. Test the reset several times. A hand that fails to return to zero is a fault you cannot fix cheaply.
How can I tell the thickness without calipers?
Photograph the watch side on next to a coin or a ruler, or compare it to a known 13 mm watch. The Portugieser case is slim for a chronograph, so extra height shows up immediately against the strap line.
Do the box and papers matter?
Not for the watch itself. Spend the budget on dial accuracy and movement quality first, and treat packaging as a separate cost. A convincing box on a poorly finished case fools nobody who handles the watch.
What should I ask before paying?
A video of the chronograph running, a photo of the date flipping, a side profile with a ruler, a macro of the dial printing, and a written return window. Five minutes of checks saves a lot of regret.