IWC · Portofino

Strap for Portofino Chronograph 39 Stainless Steel / Silver / Bracelet

Takes 20 mm straps. Verified lug width, the straps that fit this model, and answers to the most common questions.

Lug width

20mm

20 mm straps All IWC

Lug width20 mm

Case diameter39 mm

ReferenceIW3915-03 (aka: IW391503)

FamilyPortofino

MovementIWC caliber 69355 Hours, Minutes, Small Seconds | Chronograph, Column wheel

CaseStainless Steel

Spring bar

Swiss Standard universal spring bars

The right category for this model · 316L steel, all lug widths 13–26 mm

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Straps for the Portofino IW3915-03 (aka: IW391503)

Selected for the 20 mm lug width · workshop selection

All 20 mm straps →

The Portofino IW3915-03 (aka: IW391503), seen from the bench

The IWC Portofino IW3915-03 is a 39mm stainless steel chronograph exemplifying Swiss watchmaking philosophy with classical proportions and purposeful construction. Powered by the in-house IWC 69355 movement—a column-wheel chronograph with integrated moonphase, 29 rubies, and 46-hour power reserve—it delivers serious timekeeping without dimensional excess. The 20mm lug width corresponds precisely to case proportion and wrist balance, ensuring visual coherence between case and bracelet.

Frequently asked questions

What is the lug width of the IWC Portofino IW3915-03?

The lug width of the IWC Portofino IW3915-03 is 20mm. This is the only correct configuration for this model; verify the distance between the attachment lugs before ordering a compatible strap.

Which strap do you recommend for the IWC Portofino IW3915-03?

It depends on your use and aesthetic preferences. For formal occasions we recommend brown or cognac alligator; for everyday versatility, vegetable-tanned calf; for durability and patina, shell cordovan. The strap must be 20mm to ensure compatibility with the lugs.

How do you change the strap on the IWC Portofino IW3915-03?

Use a spring bar tool to push the lateral attachment pins. The pins hold the strap in place; gently slide the old strap outward, then insert the new one taking care that the pins engage completely in their respective seats.

Is a 20mm aftermarket strap compatible with the Portofino IW3915-03?

Yes, any strap with a 20mm lug width is compatible, provided the attachment pins are standard (approximately 1.8mm in diameter). The 20mm handcrafted MilanoStraps are tested for complete compatibility with this model.

How long does a leather strap last on an IWC Portofino?

A quality leather strap (alligator, calf, shell cordovan) typically lasts 3-5 years with daily wear, varying based on climate, frequency of use, and care. Vegetable-tanned leather tends to last longer than chrome-tanned. MilanoStraps offers an 18-month warranty on the structure and stitching.

The next step

The right strap isn't chosen. It is built, together.

From the atelier appointment to delivery, every step is made for those who know that things done well take time. Rare leathers, one piece at a time, eighteen months of warranty.

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Casati Milano · Via XX Settembre 15, Milan · by appointment only