The short answer

A fake IW371752 is a replica of an IWC Portugieser Chronograph. The genuine watch is a slim two-register chronograph in a case around 41mm, with a 30-minute counter at 12, small running seconds at 6, no date window, and a clean dial that leaves nowhere to hide. Replica quality on this reference swings from obvious to genuinely convincing. When I compare one against photos of the real thing, the dial print is almost never the giveaway. The movement, the case thickness, and the way the finishing catches light are what separate a decent copy from a bad one.

Why this reference gets copied so hard

Simple reasons. The design is restrained, so a factory only has to get a handful of elements right. Recognition is high, so demand exists. And the older generation of the genuine used a Valjoux-derived movement, which means the copy can be mechanically closer to the original than replicas of watches with complicated in-house calibres. That last point is why this model attracts buyers who care about how a watch runs, not just how it looks.

Check one: the movement

This is where your money goes and where most listings get vague. Three tiers exist in the market. Quartz copies run the subdials as decoration or sweep in a way that never matches a mechanical chrono. Asian 7750-based copies give you a real chronograph with a real reset, and the pusher feel is decent once broken in. Higher-tier builds use better finishing and a smoother winding action. Ask the seller what is inside, in writing. If the answer is a photo of a stock movement rather than the actual watch, treat it as a no.

Test the chrono in person if you can. Start, stop, reset. The reset should snap back to zero in one clean motion. A lazy or grinding return means the movement was assembled badly or has already been abused.

Check two: subdial spacing and layout

The Portugieser layout puts a 30-minute counter high and small seconds low, with a lot of empty dial between them. Replicas built around a movement that was not designed for this layout often push the subdials too close to the center or too far toward the edge. Look at the gap between the subdial rings and the outer minute track. On the genuine it breathes. On a cheap copy it looks cramped.

There is no date window on this reference. If a listing shows one at 3 o'clock, you are looking at a different model or a fantasy build.

Check three: case and thickness

Thin is hard. Replica cases run fat because the movement underneath is thicker than the original. Lay a copy next to a ruler and check the height at the bezel edge. Anything over roughly 13mm on a case this size reads wrong on the wrist.

Then look at the lug tops and the bezel flank. Genuine polishing has a soft transition into the brushed surfaces. Copies usually show a hard line or a slightly wavy reflection. Caseback engraving is another tell: the lettering should be crisp and evenly sunk, not shallow and rounded at the edges.

Dial, hands, and crystal

• Printing should be sharp under a loupe, with no bleeding on the brand text.
• Applied indices sit level, with even polishing on the facets.
• Hands should be the right shape for the version, feuille or baton, not a generic set.
• Anti-reflective coating on the genuine has a faint blue cast at an angle. A cheap crystal looks milky or reflects like a mirror.

Strap and hardware

Most of these ship on alligator-grain leather. Check the stitching density, the taper toward the buckle, and whether the lining is leather or synthetic. A tang buckle should be thick and well finished. A flimsy deployant is a cost-cutting signal that usually shows up elsewhere too.

Water and daily wear

The genuine is rated for splashes, not swimming. Copies are often not pressure tested at all, and the gaskets may be dry or missing. I would not take any replica near a pool, and I would get it checked by a watchmaker before trusting it in rain.

How I size up a seller

Real photos of the actual piece, including a macro of the dial and a shot of the movement through the caseback. Clear answers about the movement type. A stated return window. A price that matches the tier rather than a bargain that promises everything. Sellers who post only catalog renders usually do not have the watch in hand.

Red flags

• No photos of the caseback or movement.
• Claims of "1:1" with nothing to back it up.
• Pressure to pay outside a protected method.
• A price far below the tier the seller describes.

None of this is about spotting a fake from across a room. It is about knowing which copy you are buying, and paying for the one that matches what you actually want on your wrist.