Short answer: the phrase "Portofino moon phase 35" comes from seller listings for a copy of the IWC Portofino Automatic Moon Phase. The number 35 does not match a catalogued IWC size. IWC lists the moon phase Portofino at 37 mm, and Portofino Automatics at 34 mm. A 35 mm figure is a listing claim, not a factory number.
What the genuine watch is
IWC Schaffhausen ref. IW459401, Portofino Automatic Moon Phase 37. Stainless steel case, 37 mm diameter, about 9.5 mm thick. Moon phase aperture at 12 o'clock. Calibre 35800, automatic, 42-hour power reserve. Sapphire crystal, leather strap. IWC does not make this reference in 35 mm. Retail and secondary prices change by year and market, so current dealer listings are the only reliable source.
Moon phase: 29.53 days against 24 hours
A synodic month runs 29.53 days. The genuine moon disc steps once per day on a 59-tooth wheel, so the aperture completes one cycle in 29.5 days. Many replica movements drive the same aperture with a 24-hour day/night wheel. That disc turns once per day. The moon sits in the same position at noon and at midnight, which no real moon phase does.
Test method: note the disc position, wait 12 hours, look again. A day/night wheel shows no change. A 29.5-day wheel moves a fraction of one step and the edge of the moon shifts.
Case and movement numbers in listings
- Diameter: listings quote 35 mm to 37 mm. IWC spec: 37 mm.
- Thickness: samples run 1 mm to 2 mm thicker than the genuine case.
- Movement: Seagull ST16 or ST21, Miyota 9015, or a 2824 clone with a moon module.
- Power reserve: 38 to 42 hours on those movements. Calibre 35800: 42 hours.
- Caseback markings and rotor engravings vary between batches.
Calipers and a timing machine settle these questions. Seller photos and spec text are not measurements.
Legal status in the US
- Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320. A first offense carries up to 10 years; a second carries up to 20.
- Import of counterfeit goods is barred by 19 U.S.C. 1526. CBP seizes and destroys shipments.
- Trademark owners can sue under the Lanham Act. Statutory damages run from $1,000 to $200,000 per counterfeit mark per goods type, and up to $2,000,000 for willful use under 15 U.S.C. 1117(c).
- IWC does not service or warrant replicas. Parts do not interchange with genuine calibres.
Checks before purchase
- Measure the case. 37 mm matches IWC. 35 mm does not.
- Watch the moon aperture across 24 hours.
- Ask for the movement number and a rotor photo.
- Ask who services the watch. Independent watchmakers take the work. IWC boutiques decline it.
Genuine Portofino references trade on the secondary market. Replica resale sits near zero. Marketplaces pull replica listings when a rights holder files a complaint.