Hamilton H24515732 Ventura Open Heart AutoProduct Overview Released in 1957, the Ventura revolutionized watch history as the world's first battery powered wristwatch. The groundbreaking battery movement freed people from the act of "winding a spring." In this model, you can observe the movement of the mechanism. Specifications Product Number H24515732 Caliber H 10 Collection Ventura Movement Automatic Case Size 35mm x 54mm Thickness (mm) 11. 5 Dial Color Black Case Material Stainless Steel