Short answer
A fake Portofino moon phase is a replica of the IWC Portofino Automatic Moon Phase, a dress watch with a lunar aperture below 12 o'clock and a small date aperture. Copies come in three tiers: quartz models with a flat printed disc, automatic models with a decorative disc that spins once a day, and copies with a real moon phase module that advances roughly once every 29.5 days. Only the third tier behaves like the genuine watch. The first two look right in a photo and fail the moment you set them.
Before you compare
- Decide on case size first. The genuine family splits into a 37 mm version and a 40 mm version, and the dial layout changes with it.
- Ask the seller for full resolution photos of the dial, the crown, and the case back. Compressed marketplace images hide printing flaws.
- Set a budget. Quartz copies sit near $80 to $120. Automatic copies with a genuine lunar gear start around $300 and climb with movement quality.
- Confirm the return window in writing before payment.
How to check one step by step
- Measure the case with calipers or a ruler. A 37 mm copy that arrives at 39 mm will sit wrong on the wrist and the lugs will overhang.
- Check the thickness. The genuine watch is a slim dress piece, and thick replicas usually hide a low grade automatic movement under a spacer ring.
- Set the moon phase to a known position, then leave the watch running for 24 hours. A correct moon phase moves about one thirtieth of the way across the aperture. If the disc jumps a full step or completes a rotation, you have a day and night wheel, not a lunar one.
- Inspect the moon disc under a loupe. Good copies use a deep blue disc with two crisp moons and a faint star field. Cheap copies use a sticker with visible edges and washed out stars.
- Read the dial text. Look at letter spacing in the brand name and the city name, the sharpness of the applied indices, and whether the minute track is printed or stamped.
- Turn the crown. Winding should feel smooth with no grinding. A gritty crown usually means a dry or poorly finished movement.
- Check how the moon phase is set. On the genuine watch it is corrected through the crown. If a copy uses a hidden pusher or a recessed button on the case flank, the module is aftermarket.
- Examine the case back. Laser engraving on replicas is often shallow with rounded edges. Genuine engraving is deeper with sharper transitions.
- Test the date change. Roll the hands past midnight and watch the date flip. A slow creep instead of a snap points to a budget movement.
- Weigh the strap and clasp. Signed hardware with even brushing is a sign the rest of the watch got attention too.
Details that give a copy away
- Misspelled or oddly spaced text on the dial.
- Moon discs with cartoonish faces or asymmetric moons.
- Case backs stamped rather than engraved.
- Crowns without a logo or with a smudged logo.
- Moon phase apertures cut with a visible burr or uneven edge.
What a real lunar module costs
A working moon phase needs a 59-tooth wheel, a reduction gear, and a disc that tracks the synodic month. That is extra parts, extra assembly time, and extra quality control, which is why the price gap between a printed disc and a functioning complication is wide. If a listing claims a working moon phase at a quartz price, assume the lunar aperture is decorative. Ask the seller to send a short video of the watch running, with the aperture in frame, over a full day before you commit.