The short answer

"Portofino 35" is a search term, not an IWC model name. IWC catalogs mid-size Portofino automatics around 34 mm and 37 mm, and there is no current 35 mm reference. Sellers and forum posts use "35" as loose shorthand for the mid-size dress watch. That means two things for you. First, a listing that advertises a "35 mm Portofino" instead of a reference number deserves extra scrutiny. Second, the way to judge any mid-size Portofino is the same whether the seller says 34, 35, or 37: measure the case, read the dial under magnification, and check the movement inside.

Measure the case before anything else

Case size is the easiest place for a copy to slip. Genuine Portofino automatics are slim dress watches, and the mid-size versions stay under about 10 mm thick. Replica makers often pad the case by 1 to 2 mm to fit an off-the-shelf movement, so a watch that stands tall on the wrist or sits high in a 37 mm footprint is worth a second look. Use calipers across the case at 4 and 8 o'clock so the crown does not skew the reading. Lug width should match the reference exactly, and the crown should be proportional, signed, and turn with a smooth, even drag. A crown that feels gritty or wobbles on the stem usually points to a cheap tube and gasket.

Read the dial and hands like a printer

IWC dial printing is thin and sharp. Under a 10x loupe, the "International Watch Co." signature and the "SCHAFFHAUSEN" line should show crisp serifs and even spacing, with no paint bleed. Fakes tend to look slightly bold or slightly uneven, and word spacing drifts. The same goes for applied indices: they should sit flat, polish to a mirror, and line up with the minute track.

Hands are another tell. Genuine Portofino hands are cut and beveled, so the edges catch light differently from the flat top surface. Copies often use stamped hands that read as one flat plane. Most Portofino Automatics are pure dress watches with no luminous material, so if the hands or hour markers glow, the dial is not right. Check the date window too: the date wheel font on the genuine watch is compact and centered, and copies frequently use wider numerals that sit off-center in the aperture.

Caseback, engravings, and the movement

Engraving depth is hard to fake well. Reference and serial numbers on genuine IWC cases are cut cleanly, with uniform depth and sharp interior corners. Laser-etched numbers on copies look shallow, sandy, or slightly gray. The reference number should decode to the exact dial and case combination you are looking at, so a mismatch between the caseback and the dial is a hard stop.

The mid-size Portofino Automatic runs IWC calibre 35111, a modified Sellita SW300-1. That calibre beats at 28,800 vibrations per hour, or 4 Hz, and carries a 42-hour power reserve. Finishing is tidy but industrial: Geneva stripes on the bridges, perlage on the plates, and a signed rotor. Copies often show sticker-like decoration, sloppy jewel settings, or a rotor engraving too thick to have come from a real die. If the watch has a display back, photograph the movement and compare it side by side with a known example.

Beat rate and winding feel

Put the watch on a timegrapher, or ask the seller for a screenshot. A 28,800 vph reading with steady amplitude is what you want. Budget copies frequently run at 21,600 vph, and some quartz conversions do not belong in a mechanical Portofino at all. Hand-winding should feel smooth and slightly heavy. If the rotor spins loose like a fidget spinner or the watch rattles when you shake it, the movement is not an SW300-1.

Price, paperwork, and the seller

A mid-size Portofino sells in a set range on the secondhand market, and a discount of 60 percent or more against that range is the oldest warning sign there is. Box, papers, and service history matter less than the watch itself, but they should be consistent: booklet printing, card fonts, and the reference on the warranty card should all agree.

Buy from an authorized dealer for new, or from a seller with a written return window and documented service history for used. Ask for photos of the movement, the caseback, and the case measured with calipers. A seller who cannot or will not produce those is telling you something.

When to walk away

  • The listing calls the watch a "35 mm Portofino" and never gives a reference number.
  • The case measures more than about 10 mm thick on a mid-size automatic.
  • Dial printing looks bold, uneven, or blurred at 10x.
  • The hands or markers glow on a Portofino Automatic.
  • The timegrapher shows 21,600 vph instead of 28,800 vph.
  • Caseback engraving looks etched rather than cut.
  • The price sits far under market with no explanation.