The short answer

A fake IW371701 fails in four places: the subdial at 9 o'clock, the caseback engraving, the date window, and the movement behind the display back. The genuine watch is an IWC Portugieser Chronograph in a 40.9 mm steel case with caliber 79350 inside and subdials at 12 and 6. Work through those four points and most copies fall apart in a few minutes.

What is the IW371701?

The IW371701 is the stainless steel Portugieser Chronograph from IWC's 3717 generation, built from the mid-2000s into the 2010s. It carries a black dial with silver subdials and a date at 3 o'clock. Collectors shorten the reference to "3717".

• Case: stainless steel, roughly 40.9 mm wide
• Movement: IWC caliber 79350, automatic, based on the Valjoux 7750
• Beat rate: 28,800 vibrations per hour (8 beats per second)
• Power reserve: 44 hours
• Layout: chronograph minutes at 12, small seconds at 6, date at 3
• Crystal: sapphire with antireflective coating on both sides
• Caseback: sapphire display back
• Water resistance: 3 bar
• Strap: alligator leather on a steel pin buckle

Because the back is open, a buyer can inspect the movement without a tool. That single design choice makes the 3717 easier to authenticate than most watches in its class.

Where does a fake IW371701 give itself away?

The subdial at 9 o'clock

The 79350 in the 3717 was reworked so the small seconds sit at 6 and the chronograph minutes sit at 12. A stock Valjoux 7750 keeps running seconds at 9, a 30-minute counter at 12, and a 12-hour counter at 6. If the subdial at 9 holds a moving second hand, the watch has an unmodified 7750 and is not an IW371701.

Caseback engraving

Genuine IWC engraving is deep, sharp, and even across the whole script. The reference reads as IW371701, not 3717, and the case number is stamped to one side. Copies show shallow letters, soft edges, and wrong spacing, and many print a reference format IWC never used.

Dial, hands and date window

Real dials have applied steel numerals with polished bevels, printed text that stays crisp under a loupe, and a date window cut with square corners. Copies show fuzzy printing, flat numerals, and a date aperture with rounded or ragged edges. Check the date disc too: it should sit flush with the dial and line up with the printing.

Crown, pushers and case edges

A genuine case has sharp transitions between the brushed sides and the polished bezel, and the pushers click and return with a firm snap. Copies feel soft at the lugs, and their pushers travel with a spongy action. Run a fingernail along the lug edge on both sides of the case. Real steel bites.

How do you check the movement?

Ask the seller for a clear photo of the movement through the sapphire back. A real 79350 shows Geneva stripes, blued screws, and a rotor engraved with IWC branding, all finished by hand at the edges. Copies show a bare 7750 with stamped plates, no anglage, and sometimes a printed pattern that mimics striping.

If the seller refuses a movement photo, treat that as an answer. Legitimate sellers of a 3717 already have these images on file.

Do weight and feel prove anything?

Steel is steel, and a good copy can land within a few grams of the original. Weight alone proves little. What does hold up as evidence is the finish at the case edges, the action of the crown when you set the time, and the way the chronograph resets to zero.

What about serial numbers, box and papers?

Genuine papers list a reference, a case number, and a movement number, and all three match the watch. IWC does not run a public online lookup, so you confirm those numbers through an authorized dealer or an independent watchmaker. A full set adds value at resale, but a box and papers set can be faked as well, so it never replaces a movement photo.

Do high-grade copies of the IW371701 exist?

Yes, and they cost more than the cheap ones. They still miss on the movement, because the 79350's decoration and the subdial layout are the parts that are hardest to reproduce at a low price. Some of these builds even fit a 7750 and hide the running seconds by moving the hand, which leaves the reset behavior and the counter spacing wrong.

Frequently asked questions

Is a quartz IW371701 always fake?

Yes. The Portugieser Chronograph is a mechanical automatic watch, so a battery inside means the watch is not the reference. A quartz copy also sweeps in one tick per second instead of eight.

What is the fastest single check?

Look at the subdial at 9 o'clock. If it holds a running second hand, the watch uses the standard 7750 layout and cannot be an IW371701.

How much does a genuine IW371701 cost?

Used prices move with condition, service history, and whether the full set is present. Steel 3717 examples sit well above the price of any copy, and a full set sits at the top of the range for that model. A price far below the market is the first warning sign.

Can a watchmaker confirm a 3717 for me?

Yes, and the fee is small next to the cost of the watch. A watchmaker can open the back, read the caliber, verify the case number, and check the finishing under a loupe. Ask for those findings in writing if you plan to buy from a private seller.

Bottom line

Subdial layout, caseback engraving, date window, and movement photo cover almost every fake IW371701 on the market. Check them in that order and you filter out the weak copies before you spend real money. When a seller dodges one of those four points, walk away.