Before you pay for anything sold as an IW371788, confirm what the reference is supposed to be. It belongs to the IWC Portugieser Chronograph family: roughly 41 mm across, about 13 mm thick, with a vertical bi-compax dial (30-minute counter at 12, running seconds at 6), a date window at 3, a box-domed sapphire crystal, and an automatic chronograph movement in the 69355 family. A listing that shows a quartz movement, a 39 mm case, or subdials at 3 and 9 is not a faithful replica of this reference. It is a generic chronograph using an IWC-style dial. Treat that mismatch as your first filter, because it tells you how much care the seller puts into everything else.

What the IW371788 Should Look Like

The Portugieser line is defined by a large, open dial and a thin bezel. On the chronograph, the two subdials sit on a vertical axis, and the printed minute track runs around the outer edge. Most references in this family carry a small date at 3. The case mixes a polished bezel and lug tops with brushed case flanks. The crown sits between two pushers, and on the genuine watch the pushers have a short, crisp travel with an audible click.

Dial printing is where replicas separate. The 'IWC Schaffhausen' wordmark, the 'Automatic' line, and the chronograph text should be sharp, correctly spaced, and level. Look at the numeral at 12 and the numeral at 6, which are applied on the genuine and often glued on crookedly on cheap copies. The date window should be cut cleanly and centered, not slanted.

What to Check Before You Buy

• Case measurements: ask for caliper photos. Diameter near 41 mm, thickness near 13 mm, and a lug width that matches the strap the seller lists.
• Crystal: box-domed sapphire with an anti-reflective coating. Flat mineral glass or a pronounced blue tint is a downgrade.
• Movement: automatic chronograph, not quartz, not a faux chrono with decorative pushers. Ask for a photo of the movement and a short video of the chronograph starting, stopping, and resetting to zero.
• Dial details: subdial hand alignment, date centering, and the quality of the applied numerals. Zoom photos are more useful than wide shots.
• Caseback: correct engraving depth and a serial that matches the paperwork the seller provides, if any.
• Strap and buckle: leather or rubber that matches the reference, with a deployant or pin buckle that is finished on all sides.
• Seller terms: return window, refund method, and whether the photos you were sent are of the actual watch in stock.

Parameter Bands That Matter

Use these ranges as a checklist when you compare listings. Small deviations are common in the replica market, but large ones usually signal a lower grade build.

• Case diameter: 40.5 to 41.5 mm.
• Case thickness: 12.5 to 14 mm, depending on the movement inside.
• Lug width: confirm against the reference you are comparing. A mismatched strap is a common shortcut.
• Movement beat rate: 28,800 vibrations per hour (4 Hz) for a mechanical chronograph.
• Power reserve: a full day or more for a well-built automatic.
• Water resistance: do not assume more than splash resistance unless the listing states a rating and the caseback gasket is visible.

Common Pitfalls

The largest risk is not the watch itself. It is buying from a seller who uses photos of a different watch. Reverse image search the listing photos. Ask for a timestamped photo with the watch and a handwritten note. If the seller refuses, move on. Other frequent problems:

• Stock photos of the genuine watch with no actual product shots.
• 'Swiss made' claims paired with a movement that has no Swiss markings.
• Chronograph pushers that do not function, or a chronograph seconds hand that stutters.
• Subdial hands that do not reset to the 12 marker.
• Misspelled or poorly spaced dial text.
• No return policy, or payment methods with no dispute process.

FAQ

Is the IW371788 a current reference?

The IW3717 family covers several Portugieser Chronograph references released over a span of years. Specific numbers come and go as IWC updates dial colors and case options. Check the reference on the caseback against the dial configuration before you assume a listing is accurate.

How do I tell a replica from the genuine watch?

On a real Portugieser Chronograph, the movement finishing is clean, the rotor engraving is crisp, and the crown and pusher action is precise. Replicas often show rough movement finishing, shallow engraving, and a looser winding feel. If you can handle the watch, compare the weight and the sound of the rotor.

Do all replicas use a working chronograph?

No. Some use a quartz module with decorative pushers, and others use a mechanical chronograph movement that works. That difference affects price and reliability, so ask directly and ask for video.

What should I ask before paying?

Ask for photos of the exact watch, a video of the chronograph running, movement photos, caliper measurements, and the return terms in writing. If any of those are missing, the risk sits with you.