Short answer
A replica Portofino Moon Phase 35 is a copy of the IWC Portofino Automatic Moon Phase. IWC lists that model with a 37 mm case. A listing that says 35 often means the seller measured 35 mm to 36 mm at the bezel, or the seller carried a wrong number across from another listing. Ask for a photo of the case under digital calipers before you pay. If the measured width is 35 mm, the crown, strap and dial proportions will not match the original part for part.
What the original is
The Portofino Automatic Moon Phase 37 is a dress watch. Steel or rose gold case, slim lugs, round bezel, sapphire crystal. IWC lists caliber 35800 inside, a self-winding movement with a moon phase module. The dial has applied indices, leaf hands, a moon phase aperture and a date window. Dial colors include silver-plated, blue and slate, and date placement changes between references. Check the layout against the exact reference number you want. Do not trust one photo to cover every version.
Case size and what to measure
Ask for calipers across the case at 3 and 9 o'clock, then at 12 and 6. Ask for the case thickness, the lug width and the strap taper. Replica straps come in odd sizes, and a third-party replacement is sold by lug width. A wrong number costs you a strap. Ask for the crown diameter and a side view of the crown guards. Wide gaps between the crown and the case point to a mismatched case set.
Movement and moon phase
A correct moon phase runs on a 59-tooth disc that carries two moons. One full cycle takes about 29 days, 12 hours and 44 minutes. Cheap copies print one moon on a disc that steps once a day with the date wheel. Test the disc: shoot the aperture at the same hour on two days and compare. The disc should move about 1/29.5 of a turn per day. Check that both moons sit centered in the aperture and at equal depth from the rim. Dust, smears and off-center printing show up in macro shots.
On the original, the middle crown position sets the date and the moon phase. Copies vary. Some use a pusher, some use a recessed corrector on the caseback, some set the moon phase with the crown at the second position. Ask for a video of all crown positions before you buy.
Checks before payment
- Dated photos or a live video, not stock images.
- Calipers across the case, 3 to 9 o'clock.
- Moon phase disc: clean printing, centered moons, no dust.
- Date flip: set the watch to 11:55 pm and watch the change.
- Caseback engraving: depth of text, spelling, reference number.
- Strap: grain, stitch count, buckle finish, spring bars.
- Crown: winding feel, no grit, thread engagement on screw-down types.
Care and setting
Do not set the date between 9 pm and 3 am. The date train sits engaged in that window and a forced turn can shear a tooth. Set the moon phase by counting days from the last new moon, one step per day. Wind a stopped watch about 20 turns before you set the time. Keep the watch away from water. Most copies carry no tested water resistance and no gasket spec. Movement service for replica calibers runs short, often 2 to 4 years when the watch runs every day.
Price and grade
Price does not track quality on this model. Sellers label grades with factory names, and the same factory name can cover two builds. Two watches at one price can differ in dial print, hand polish and case finish. Ask what movement is inside: a decorated clone of the IWC caliber, a quartz moon phase module, or a Chinese automatic with a moon phase disc. Buy from a seller who stocks spare crystals and crowns for the case you order.