Quick Answer
A fake IW371490 is a replica of the IWC Portugieser Chronograph reference IW371490. The genuine watch is a 41 mm stainless steel chronograph with a 30-minute counter at 12 o'clock, small seconds at 6 o'clock, a date window at 3 o'clock, leaf-shaped hands and a screw-in caseback. Most replicas copy the outline but slip on one of five details: case thickness, subdial position, date font, hand finish, or movement beat. The checks below tell you which one you are holding.
Replica Tiers You Will Meet
- Low tier: quartz movement, flat printed subdials, wrong case proportions.
- Mid tier: automatic movement with a decorated rotor, correct diameter but wrong thickness.
- 1:1 tier: cloned or modified automatic calibre, matched case profile, matched date font and deep engraved caseback.
Prerequisites
- 10x jeweler's loupe
- Digital calipers
- Gram scale accurate to 1 g
- Bright diffused light and a neutral background
- High resolution photos of a genuine IW371490 dial and caseback, plus the reference spec sheet
How to Inspect a Replica IW371490
- Place the watch under the loupe and read every line of dial text before you touch anything else.
- Measure the case diameter across the bezel and the total thickness with the calipers.
- Compare the subdial centers: the 30-minute counter sits at 12 and the small seconds at 6.
- Check the date window at 3 for square edges, a centered numeral and the correct font weight.
- Study the hand shapes for a leaf profile, polished flanks and clean tips.
- Look at the crystal edge for anti-reflective coating on the inner surface alone.
- Turn the watch over and read the caseback engraving, reference number and serial.
- Press the upper pusher to start the chronograph, then the lower pusher to reset it.
- Weigh the watch on the scale and compare the number to the reference figure.
- Inspect the strap, buckle or folding clasp for engraving depth and edge finish.
Red Flags That Expose a Low-Tier Copy
- Subdials that sit too far from the dial center or crowd the outer track.
- A date numeral that touches the window frame or sits off center.
- Case thickness above the genuine figure, which pushes the caseback off the wrist.
- A seconds hand that stutters or ticks once per second, a sign of a quartz module.
- Chronograph reset that snaps the hand to the wrong index.
- Caseback text in thin laser print instead of deep engraving.
What Separates Premium 1:1 From the Rest
Premium builds match the reference in four areas: case profile and lug curve, dial print and subdial geometry, hand finish, and a movement beat rate of 28,800 vph. Ask the seller for macro photos of the dial, the caseback and the running movement before you pay. A seller who cannot supply them is offering a mid-tier watch behind a premium listing. On the wrist, the test is simple: the pushers should feel firm with a short travel, the rotor should spin with a light wrist turn, and the date should flip at midnight without a visible drag.