Hamilton Watch Jazzmaster Open Heart Auto 42mm H32705140. Offering a glimpse of its powerful inner mechanics, the Jazzmaster Open Heart lets precision take center stage with a new 42mm dial. Featuring a captivating midnight blue dial that sparkles, this showstopping timepiece fuses the modernity of urban architechture with the infinity of the cosmos. Showcasing Hamilton's ever-evolving craftsmanship and attention to detail, the dial brings the H-10 automatic movement into the spotlight. With its 80 hour power reserve and Nivachron balance spring, the Jazzmaster Open Heart Auto is fitted with an intricate stainless steel bracelet. Discover our collection of dress watches.