A fake IW371752 is a counterfeit of IWC's Portugieser Chronograph reference, and the quickest way to catch one is to compare dial print, subdial spacing, caseback engraving, and movement finishing against confirmed photos of the same reference. Most fakes fail on two or three of those points at once, so one odd detail is worth noting but two is a pattern. The guide below walks through what each check looks like in practice, plus what to do when you cannot inspect the watch in person.

What the IW371752 Reference Actually Is

IW371752 belongs to the IW3717xx block, the reference family that covers IWC's Portugieser Chronograph with the two-register dial layout. That matters because counterfeiters copy the outside of a watch, not the reference history. If a seller cannot tell you which generation of the Portugieser Chronograph they are offering, you already have a reason to slow down.

Two generations sit behind most listings:

• Earlier IW3717 references used a 79350 calibre, a chronograph movement built on a Valjoux 7750 base.
• Newer 41 mm Portugieser Chronograph models use IWC's in-house 69355 calibre.

Know which one you are supposedly buying before you judge the movement, because the correct answer changes what the back of the watch should look like.

The Five Checks That Catch Most Fakes

1. Dial print and subdial spacing

The Portugieser Chronograph has a clean dial with applied numerals, thin feuille hands, and subdials at 12 and 6. On a fake IW371752 the printing usually looks slightly heavy or slightly soft, the minute track can drift, and the subdial rings often sit a fraction off centre or measure a hair too large. Look at the space between the outer track and the case edge. On genuine examples that gap is even all the way around. On copies it usually is not.

2. Case finishing and pusher feel

Run a fingernail along the case flank and the lug edges. Genuine polishing and brushing meet at a crisp, defined line. Repolished or faked cases feel rounded and vague, and the transition between finishes smears. Then press the chronograph pushers. Real pushers have a short, positive travel and a clean reset. Cheap copies feel spongy, gritty, or need a second push to snap back to zero.

3. Caseback engraving and reference numbers

Reference and serial numbers should be engraved, not laser-printed on a sticker, and the lettering should be consistent in depth. Fakes commonly use shallow etching that catches light unevenly, and the numbers themselves often do not match the dial variant. Photograph the caseback with a phone at an angle and zoom in. Soft, rounded letter edges are a strong signal.

4. Movement and winding feel

Wind the watch slowly and listen. A Valjoux 7750 based calibre has a distinctive feel and a rotor that spins freely in one direction with a light whir. Replica movements often feel tight, sound tinny, or use a decorated plate that imitates finish without matching the layout. If the seller will not show a movement photo with the caseback off, treat the listing as unverified.

5. Strap, buckle, and weight

Strap hardware is where corners get cut first. Genuine buckles are solid, sharply stamped or engraved, and the leather has a firm, dense hand. Fakes often use lightweight hardware with soft engraving and leather that creases sharply within days.

Why Photos Alone Are a Weak Test

Marketplace photos are compressed, colour-shifted, and often borrowed from other listings. A reverse image search takes ten seconds and catches a surprising number of fraudulent ads. Ask for a dated photo of the caseback with the watch set to a specific time. If the seller resists, the answer is already there.

Seller Behaviour and Paperwork

• Pricing far below the going rate for the reference, with a story attached.
• No service history, no box, no booklet, and a vague explanation for all three.
• Pressure to pay by bank transfer or a peer-to-peer app with no recourse.
• Serial numbers cropped out of every photo, or a serial that does not appear on the warranty card.

Any one of these can be innocent. Three together is a pattern.

If You Are Knowingly Buying a Replica

Some buyers search for a fake IW371752 because they want a replica, not an authentic watch. Be clear with yourself about the trade-offs: replica chronographs rarely hold accuracy, water resistance is not what the engraving claims, and service support is close to zero. Buy from a seller who shows real photos of the actual unit, states the movement inside, and offers a return window. A listing that uses stock images of the genuine watch tells you nothing about what will arrive.

How to Get a Real Verdict

An authorised IWC retailer or a watchmaker who services the brand can confirm authenticity in minutes with the caseback off. If the watch is being sold remotely, make authentication a condition of the sale and use an escrow style payment. For a piece at this price point, that step costs very little compared with the alternative.