Short answer
IW371640 sits in IWC's Portugieser Chronograph 41 block. The real watch is a 41mm steel chronograph with IWC's own automatic movement and a two-register dial. Replicas of it split into three rough tiers. Under about $250 you get quartz, mineral glass, and a case that runs a millimeter or two fat. Between $350 and $500 at the top tier you get sapphire, a decent strap, and a Valjoux-derived automatic that reads correctly on the wrist. I only bother with that top tier. Everything below it is a costume, not a watch.
What the genuine reference is
The IW3716 line replaced the long-running IW3714 Portuguese Chronograph, which used a modified Valjoux 7750 and measured 40.9mm. The newer 41mm version runs IWC's calibre 69355 from the 69000 family, with a 46-hour power reserve. Case thickness lands near 13mm, water resistance is 3 bar, and there is no date window. The layout is pure Portugieser: running seconds at 6, a 30-minute chrono counter at 12, deeply recessed subdials, a thin bezel, and a lot of empty dial.
That empty dial is the problem for fakes. Blank space punishes sloppy printing, and there is nowhere to hide a marker that sits half a degree off.
One practical note. Reference numbers inside this block cover several dial, hand, and strap combinations, so confirm the exact configuration you are being offered against IWC's own listing before you compare details. Two watches from the same block can look nothing alike.
How the replica tiers break down
Tier one is quartz with a decorative chrono. The pushers feel like buttons on a TV remote, and one subdial usually does nothing. Skip it.
Tier two is the budget automatic, most often a stock or lightly modified 7750. Case edges feel sharp, the crown is undersized, and the caseback is a plain disc with shallow engraving. It tells time, which is the whole compliment I can give it.
Tier three is what sellers call super clone or 1:1. Correct 41mm case, sapphire front and back with inner anti-reflective coating, applied markers with clean edges, and a real chronograph movement with a decorated rotor. This is where the subdial positions finally match the real thing.
Movement reality check
Here is the detail most buyers miss. IWC's calibre 69355 puts the small seconds hand at 6 o'clock. A plain Valjoux 7750 puts it at 9. So any maker who wants the dial to look right has to start from a modified base or build a module on top. Ask the seller which movement base is inside and how the running seconds were moved. If the answer is vague, assume it was not addressed, and expect a subdial sweep that stutters or a hand in the wrong spot.
Expect to service it eventually. Any competent watchmaker can handle a 7750 base for $120 to $200, but IWC will not touch it, and there is no factory warranty to fall back on.
Tells that matter more than the logo
- Case thickness. Around 13mm on the real watch. At 14.5mm the caseback sits proud and you get a visible gap where the strap meets the lugs.
- Subdial depth and spacing. The genuine subdials are cut down into the dial with a soft shadow line around each one. Flat printed rings are a giveaway.
- Print quality. The branding should show crisp letter edges and even spacing under a loupe. Ink bleed or a wavy baseline is common on mid-tier builds.
- Crystal. Flat mineral glass has no coating and picks up a grey cast when you tilt it. Sapphire with inside coating nearly disappears at an angle.
- Pushers. Genuine chrono pushers have a short, firm throw with a positive click. Mushy travel means a cheap movement or a worn spring.
- Strap. The real watch ships on alligator. Most replicas ship on embossed cowhide that cracks at the buckle within months. Budget $60 to $120 for a replacement.
- Caseback. Reference number, crystal marking, and rotor decoration should all be sharp and aligned. Blurry laser etching reads as fake from across a table.
Water resistance and daily wear
3 bar on the real reference means splashes only. On a replica the gaskets are a lottery, so treat it as not water resistant at all. No swimming, no showering, no dishes. Wipe it with a soft cloth instead and keep it away from soap, which eats rubber seals over time.
What I check before paying
- Ask for a video, not photos. Run the chrono start, stop, and reset, and watch the subdial hands sweep back to zero.
- Get the movement base in writing, including how the small seconds were relocated.
- Request a caliper shot on the case flank so you can confirm thickness yourself.
- Check the return window. Anything shorter than seven days is a red flag.
- Look up the dial variant you are being sold. If that combination does not exist in the official catalog, you are buying a fantasy piece.
Bottom line
A replica IW371640 is worth owning only if the case is 41mm, the crystal is sapphire, and the movement keeps the subdials where IWC put them. Pay for those three things and the watch holds up. Save the money and you are buying a shape, not a chronograph.