IWC, Portuguese series, model: IW390502, automatic mechanical movement, stainless steel, case diameter: 43.5MM • Silver-white matte dial, black Arabic numeral hour markers, and the signature red central chronograph seconds hand (a distinctive feature of the Marine series) • Dual sub-panel layout: ◦ 12 o 'clock position: 12-hour chronograph accumulation dial ◦ 6 o 'clock position: A countdown sub-plate for sailing boats, printed with the words "YACHT CLUB", used for the countdown of sailing events • Single-window calendar display at the 3 o 'clock position, with a nautical timing scale track on the outer circle Strap: Black anti-slip rubber strap, waterproof and sweat-resistant, suitable for water, leisure and light business scenarios. Equipped with the IWC self-produced Cal.89365 flyback automatic chronograph movement, featuring 38 gemstone bearings With a vibration frequency of 28,800 times per hour and a power reserve of 68 hours, it has a significant advantage in long battery life • Flyback timing function: The timing resets to zero without stopping the watch. One-click reset is a practical feature specifically designed for sailing events. The transparent back cover shows high-quality hand-polished finishes.