A good replica of the IWC Portofino Automatic 37 stands or falls on three measurements and one number. The case must measure 37 mm across, the profile must sit near 9.5 mm thick, and the movement must beat at 28,800 vibrations per hour. Nail those and the watch wears close to the original. Miss them and no amount of polished finishing hides the gap.

Reference specs to compare against

Know the target numbers before you look at photos. The genuine Portofino Automatic 37 (reference IW4586 family) sets these benchmarks:

  • Case diameter: 37 mm, measured across the case body, crown excluded.
  • Case thickness: roughly 9.5 mm, which is what keeps it under a shirt cuff.
  • Movement: Caliber 35111, built on the Sellita SW300-1, 28,800 vph, about 42 hours of power reserve.
  • Crystal: sapphire with anti-reflective coating on both faces.
  • Water resistance: 3 bar in the factory specification.
  • Strap: slim profile leather with a signed pin buckle.

Inspection steps

  1. Ask the seller for caliper photos of the case diameter and thickness before you agree on a price.
  2. Measure the case yourself when it arrives. A 39 mm or 40 mm body is a different watch, not a small deviation.
  3. Measure the thickness at the crystal edge. A copy that runs 12 mm thick sits tall on the wrist and reads as fake at arm's length.
  4. Set the watch next to the reference photo and compare the lug shape and curve. The Portofino lug is short and tapers toward the strap.
  5. Examine the dial print with a loupe. Check the logo lettering, the word AUTOMATIC, and the spacing between the date window and the markers.
  6. Look at the date wheel font. Thin, wrong-shaped numerals are the most common give-away on this model.
  7. Check the hands under light. The leaf-shaped hour and minute hands should have flat, even polishing with no burrs at the tips.
  8. Wind the crown and set the time. It should advance smoothly with no grinding and the hands should not jump when you push the crown back in.
  9. Time the movement over 24 hours against a reference clock. Anything worse than 15 seconds a day needs regulation or a return.
  10. Inspect the rotor through the caseback. Look for clean engraving and no loose screws or metal filings.
  11. Flex the strap and check the buckle tang. Soft, shiny leather is a fast tell.
  12. Confirm the return window in writing before payment, then keep the packaging until you finish testing.

Movement options you will see

  • Quartz: sweeps in one-second ticks. Not worth considering for this model.
  • Miyota 8215: reliable, but 21,600 vph, so the seconds hand moves in a visibly slower sweep.
  • Miyota 9015: 28,800 vph and roughly 42 hours of reserve, which matches the genuine beat rate and is the best value base.
  • Decorated Sellita SW300 or clone 35111: closest to the original in beat rate, rotor markings, and winding feel.

What no replica delivers

There is no manufacturer warranty, no service from an authorized repair center, and almost no resale value. Water resistance on a copy is a claim, not a test result, so keep it away from pools and showers unless a watchmaker pressure-tests it first. A Miyota 9015 base is easy for any independent watchmaker to service, which matters more over five years than a decorated rotor. Last, check the rules where you live: import and sale of replica watches is restricted in many countries, and that risk sits with the buyer.

The short version

Measure the case, verify the beat rate, read the date font, and buy only from a seller who takes returns. If the diameter and thickness match and the movement runs at 28,800 vph, you have the best version of this replica currently made.