The IW3270 reference is the 40 mm IWC Pilot's Watch Mark XVIII, and a first-copy version stands or falls on three details: the 40 mm case footprint, the matte black dial with white printed numerals at 12, 3, 6 and 9, and a movement built to the caliber 35111 pattern with a 42-hour power reserve. Verify those three first. Then work through the crown, the case back and the strap. The steps below run in that order.

Prerequisites

  • Reference photos of the genuine IW3270 from at least two angles
  • A caliper or a ruler with millimeter marks
  • A loupe or a phone with a macro lens
  • A clock or phone timer for the power-reserve test

Step 1: Confirm the case size

  1. Measure the case across the bezel at the 9 to 3 line without the crown.
  2. Confirm the reading sits at 40 mm, with no more than 0.3 mm of drift.
  3. Measure the thickness from the crystal top to the case-back center and confirm it lands near 10.8 mm.
  4. Check the lug width at 20 mm so standard straps fit.

A seller who quotes 42 mm or 44 mm is describing a different Pilot's model, not the IW3270.

Step 2: Read the dial under magnification

  1. Check that the Arabic numerals at 12, 3, 6 and 9 are printed, not applied, and sit flat against the dial.
  2. Confirm the triangle at 12 carries two dots and aligns with the center line.
  3. Look at the date window at 3 and confirm the aperture edges are cut sharp, with the disc centered.
  4. Inspect the sword hands for even lume fill and a clean sweep second hand with no burr at the tip.
  5. Confirm the dial is matte black with no sunburst or gloss.

Step 3: Test the movement and crown

  1. Wind the crown 30 turns and confirm the rotor spins freely when you tilt the watch.
  2. Set the time and date, then check that the date flips within 10 minutes of midnight.
  3. Run the watch for 24 hours against a reference clock and note the daily rate.
  4. Let it sit unworn and confirm it keeps running past the 40-hour mark.

A healthy copy holds within roughly 10 to 20 seconds a day. Anything past 45 seconds a day points to a poorly regulated movement.

Step 4: Inspect the case back and strap

  1. Confirm the case back is solid steel with an engraved motif, not a glass display back.
  2. Check the engraving depth and lettering alignment with a loupe.
  3. Flex the strap and confirm the leather is stitched, not glued, at both ends.
  4. Operate the pin buckle and confirm the tang seats square in the hole.

Step 5: Ask the seller four questions

  • Which movement is inside, and what is the stated power reserve?
  • Is the crystal sapphire or mineral glass?
  • What is the stated water resistance, and was it pressure tested?
  • What is the return window if the case measures off spec?

Ask for a photo of the watch on a caliper next to the reply. Sellers who cannot supply one are usually working from a catalog image.