The short answer

The IW371435 is a 41mm IWC Portugieser Chronograph in stainless steel with a silver-plated dial, gold-plated hands and appliqués, two subdials, no date, and a black alligator strap. A replica worth owning should match all of that on the wrist and under a loupe. If the case measures wrong, if the subdials are arranged in the wrong order, or if the small seconds hand steps once per second, stop there. Those three checks catch most of the bad builds before you ever look at the movement.

Case and dimensions

Measure the case across at 2 and 8 o'clock, without the crown. You want 41mm, plus or minus a fraction. Thickness should land near 13mm on a calibre 79350 style build, and the lug width is 20mm. The genuine watch has a polished bezel and polished caseband, a fairly slim bezel, and long, gently curved lugs that let the watch sit flat on a 7 inch wrist.

I look for these things in order: lugs that taper the same amount on both sides, a crystal that sits flush with no gap at the edge, and a crown that screws down without grit. A crown that wobbles or a bezel with a visible seam under the crystal usually means the case was rushed.

Dial details

This reference is a two-register chronograph. The running seconds sits at 6 o'clock and the 30 minute chronograph counter sits at 12. That layout matters because the base movement used in most builds is a Valjoux 7750 style calibre, and the subdial positions are the first thing cheap factories get backwards.

  • The 6 o'clock subdial must sweep smoothly as a running seconds hand.
  • The 12 o'clock counter should jump one increment per minute while the chronograph runs.
  • There is no date window on this reference. An aperture at 3 o'clock is an instant giveaway.
  • Numerals and hands are gold-toned on a silver-plated base, with a fine circular graining in both subdials.
  • Print should be crisp and level: brand name and SCHAFFHAUSEN centered below 12.

Under magnification, look at the minute track. On a good dial the divisions are sharp and evenly spaced all the way around. On a poor one they get crowded near 12 and blurry near 6, which is where cheap pad printing fails.

Movement and winding feel

A mechanical build should feel alive in the hand. Wind it slowly and you want a light, even resistance. It should not feel like you are grinding sand. Push the top pusher: the chronograph seconds hand should start cleanly, with a firm click, and the reset pusher should snap the hand back to zero in one motion rather than drifting.

The easiest tell from across a table is the sweep. At 28,800 vibrations per hour the seconds hand moves in eight small steps per second, which reads as a smooth glide. A quartz build ticks once per second. If you cannot see the watch running, ask for a video with the chronograph engaged.

Strap, buckle, and caseback

The genuine watch ships on black alligator with a signed pin buckle, and the caseback is solid rather than a display back. That solid back is helpful. It means you are not paying for movement decoration you will never see, and it means the engraving quality is the thing to inspect: reference number, engraving depth, and lettering that is centered rather than crooked.

Check the strap too. Good alligator-embossed leather has a visible scale pattern that changes direction and size across the strap. Flat, plasticky leather with identical scales is a fast sign of a budget package.

Red flags to walk away from

  • Case diameter off by more than half a millimeter.
  • A date window, or a subdial swap that puts the chronograph minutes at 6.
  • Seconds hand that ticks once per second.
  • Pushers that feel mushy or do not click.
  • Hands that are too short, too thick, or painted instead of applied.
  • Crooked printing under 12, or a logo that sits off center.

What to expect from the finish

Be realistic. A replica can look very close at arm's length, and a well built one can fool most people in a room. It will not match the movement finishing, the hand-polished bevels, or the long term service record of the real thing. Movement finishing on a replica is often brushed and plain, and parts availability years down the road is a gamble.

Treat it as a wearable look, not an investment. Buy it because you like the dial, not because you expect it to hold value.

Care after you buy

Keep it dry unless the seller has actually pressure tested it. A 30 meter rating is splash resistance at best, so take it off for swimming, showers, and washing dishes. Wind it gently once a week if it sits, and have a watchmaker look at the movement every few years. Storing it on a soft cloth rather than a hard box keeps the polished case free of hairline scratches.

Buy the build, not the photos. Ask for the three measurements, a video of the chronograph running, and a clear shot of the dial printing. If a seller cannot or will not send those, that answers the question for you.