Quick answer
IW371653 is an IWC reference in the Portugieser Chronograph family. The 3716 case measures 41 mm and holds an automatic chronograph movement. Counterfeits of this reference come in two grades: a cheap quartz version and a "super clone" with an automatic movement and a copied dial. The reliable tells are the movement under the sapphire caseback, the date font, the subdial spacing, and the caseback engraving. No single photo proves a watch is genuine.
What the reference number means
IWC builds reference codes from three parts. The IW prefix marks the brand. The four middle digits mark the case and movement family. The last two digits mark the dial, hand, and strap combination for a market and season.
- IW: IWC Schaffhausen.
- 3716: Portugieser Chronograph, 41 mm, steel, two registers.
- 53: dial and strap code assigned by IWC.
IWC does not publish a complete historical reference list. A public catalog entry for 371653 is not easy to confirm, so the exact factory dial and strap combination is unknown here. IWC customer service can confirm it from the number if the request is sent in writing.
Movement check
Current 3716 watches run calibre 69355. It is an in-house automatic with a column wheel, 46 hours of power reserve, and a 4 Hz beat rate. The rotor is skeletonized and carries the Probus Scafusia medallion. Earlier 3714 watches used calibre 79350, a Valjoux 7750 base.
Most counterfeits run a Seagull ST19 or a 7750 copy. Rotor text on those movements is printed, not engraved. Printed text fades and smears. Finishing on a copy shows milling marks on the bridges. The genuine bridge has Geneva stripes and polished bevels.
Case and dial tells
- Case thickness. The genuine 3716 is about 13 mm. Copies run 14 mm to 15 mm and sit higher on the wrist.
- Subdials. Small seconds sits at 6 o'clock. Chronograph minutes sit at 12. Copies shift these centers by 0.5 mm or more.
- Date window. The aperture edge is chamfered on the genuine dial. Copies leave a sharp, flat cut.
- Applied numerals. Genuine markers sit level and polished. Copies show glue residue at the base.
- Crystal. Genuine sapphire has anti-reflective coating on both faces with a faint blue tint. Copies show heavy purple or green flare under light.
- Weight. A steel 3716 on a leather strap weighs about 90 g. Copies differ by 10 g or more in either direction.
Caseback and serial
IWC engraves the reference number and a serial number on the caseback. Newer serials have seven digits. The engraving is cut into the metal with crisp edges. Counterfeits use laser etching with shallow, rounded edges, or acid etching that looks gray and uneven. Check the medallion relief depth and the space between characters.
What photos cannot prove
A dial photo cannot confirm a movement. A movement photo cannot confirm a case. A service record from IWC is the only proof of origin. If a seller refuses an in-person inspection by a watchmaker, treat the watch as unknown.