Short answer

Almost every listing tagged "IW371654" is a replica of IWC's Portugieser Chronograph, a 41mm steel watch with a column-wheel chronograph, a 30-minute counter at 12, small seconds at 6, and no date. A serious replica gets the dial layout, the case profile and the pusher feel right. A cheap one misses all three. Judge the watch on those points, not on the box, the card or the shrink wrap.

What the genuine reference is

The IW3716 family replaced the older 3714 line, so most of what you'll compare against is the modern 41mm Portugieser Chronograph. The numbers that matter when you're grading a copy:

• 41mm stainless steel case, roughly 13mm thick, with a narrow polished bezel
• In-house calibre 69355, column wheel and vertical clutch, about 46 hours of power
• Bicompax layout: 30-minute totalizer at 12, running seconds at 6
• Feuille (leaf) hands, applied indices, printed minute track, no date window
• Sapphire front and back, display caseback, 30m water resistance

That lack of a date is one of the reasons this reference is copied so heavily. No date wheel means no misaligned calendar window to give away a fake, and the two-sub-dial layout hides the movement behind the dial less than you'd think.

Why the IW371654 gets copied

It's a clean, readable chronograph with a well-known name, and it doesn't rely on complications that are hard to fake. The dial is mostly flat, the indices are simple, and the hands are thin. Get those right and a photo will look convincing. The hard parts, the parts that separate a $180 copy from a $600 one, sit in the pushers, the crystal and the movement finishing you only see with the watch off your wrist.

The three replica tiers you'll actually see

Budget tier

Quartz or a basic automatic with a modular chrono. Sub-dial spacing looks off, the running seconds hand ticks instead of sweeping, and the pushers feel like a ballpoint pen. The dial is often too glossy and the hands are stamped, with blunt tips.

Mid tier

Clone or modified automatic chronograph. Correct sub-dial positions, decent brushing on the case, sapphire crystal with some anti-reflective coating. The chronograph usually starts and stops fine but resets with a soft thud rather than a snap.

Top tier

Closer to the 69355 architecture, sometimes with a column wheel. Pusher travel is short and crisp, the reset snaps back instantly, and the caseback engraving uses the correct font weight. This is the tier worth paying for if you care about how the watch feels on the wrist rather than how it looks in a photo.

Dial and sub-dial tells

I look at the minute track first. On a good copy the printed hash marks are sharp under a loupe and evenly spaced all the way around. On a weak one they smear or thin out near the date-less 3 o'clock position. Then the sub-dials: the 30-minute counter should sit dead center under 12, not drifting left. The feuille hands should taper to a point with no burr on the edges, and the applied indices should catch light the same way on both sides of the dial.

Case, pushers and the chronograph test

Run the chronograph before you buy. Start it, let it run twenty seconds, stop it, then reset. A proper column-wheel or vertical-clutch setup resets with a clean snap and both hands fly back to zero together. If the minute counter lands a hair off zero, or if the pusher feels gritty in the middle of its travel, that's a mechanical tell you can't photograph away. Check the lug profile too. The Portugieser lugs are thin and curve down sharply, and cheap cases get this chunky and flat.

Questions worth asking a seller

• Which movement is inside, and is the chronograph a column wheel or a modular add-on?
• Are the photos of the actual watch, including a close-up of the caseback engraving?
• What is the measured case diameter and thickness with calipers?
• Does the chronograph reset to zero cleanly, and can you send a short video of it?
• What is the return window if the pushers or sub-dials turn out wrong?

Bottom line

The IW371654 is easy to fake on paper and hard to fake in the hand. Dial layout and case shape get you most of the way, but the pusher feel, the reset snap and the crystal clarity are what separate a watch you'll enjoy wearing from one you'll notice every time you press the top button.