Quick Answer
A genuine IWC IW371615 is a 41 mm stainless steel Portugieser Chronograph with a blue dial, a 30-minute counter at 12 o'clock, running seconds at 6 o'clock, no date window, and the in-house calibre 69355 visible through a sapphire caseback. Most fakes give themselves away in the same four places: an extra date window, subdials in the wrong position, a Valjoux 7750-based movement behind the glass, and caseback engraving that does not match the guarantee card.
Prerequisites
- A loupe, or a phone camera with a macro mode
- A caliper or a ruler that reads in millimeters
- Daylight or a bright, diffuse lamp
- Seller photos of the caseback, the movement, and the paperwork
Step-by-Step Checks
- Confirm the dial layout. Look for two subdials, at 12 and at 6, and no date window. Applied Arabic numerals sit at 12 and 6, with applied batons for the other hours. A date aperture at 3 or 4:30, or a subdial at 9, rules the watch out as an IW371615.
- Measure the case. Run a caliper across the bezel, away from the crown. The genuine case is 41 mm wide and about 13.1 mm thick, with 20 mm lugs. Fakes often run 1 to 2 mm wider and sit taller on the wrist.
- Study the hands. The leaf-shaped hour and minute hands reach the printed minute track. When the chronograph resets, the central seconds hand returns to 12 and stops there. A hand that rests a few degrees off zero points to a cheaper movement.
- Inspect the crystal. Sapphire with an anti-reflective coating on both faces keeps the dial readable at an angle, with a faint blue tint. Mineral glass on a fake reflects more light and scratches with normal wear.
- Read the caseback engraving. Genuine engraving is crisp and even in depth: the model name, IW371615, the case material, and an eight-digit serial number. Fakes show shallow, rounded lettering and a serial that repeats across listings.
- Examine the movement. Through the display back you should see calibre 69355: a column wheel, Cotes de Geneve stripes, blued screws, and a rotor engraved with the IWC Probus Scafusia mark, rated at 46 hours of power reserve and 28,800 vibrations per hour. A plain rotor or a wobbling rotor means a fake.
- Test the chronograph. Press the top pusher. The start is crisp and the reset snaps back with a firm click. A 7750-based fake feels spongy, and its subdial at 9 runs the seconds, which the real watch does not have.
- Check the bracelet and clasp. The IW371615 ships on a stainless steel bracelet. Look for solid links, brushing and polishing that meet in clean lines, tight end links with no gaps, and a folding clasp engraved with the IWC logo.
- Match the serial to the paperwork. The eight-digit serial on the caseback must match the guarantee card and the booklet. Ask for one photo showing the caseback and the card together.
- Compare the price. Genuine examples trade in the thousands of dollars. An asking price in the hundreds is the shortest answer you will get.
Red Flags That Confirm a Fake
- A date window anywhere on the dial
- A running-seconds subdial at 9 o'clock
- A case wider than 41 mm or noticeably thick
- A rotor with no engraving, or one that rattles when the watch is tilted
- A serial number that appears in another online listing
- A guarantee card with a reference or serial that does not match the case
- Numerals that are painted rather than applied, flat under a loupe
- Pushers that stick, or a chronograph hand that resets off zero
When to Get Expert Verification
If the dial, case, and paperwork all line up but you still have doubts, take the watch to a watchmaker and have the caseback removed. A look at the movement settles the question in minutes. An IWC boutique or authorized service center can also confirm a serial number against its records. For any purchase in the thousands, ask for the service history and buy from a seller who accepts a return after inspection.