Based on Seiko's Speedtimer models from the past, the SPB513 combines sports timing heritage with modern mechanical precision. The hairline-finish silver dial features a countdown timer ring for measuring event duration, accented by an orange-tipped second hand, date calendar, and LumiBrite hands and markers for low-light visibility. Inside is a 24-jewel automatic movement beating at 21,600 vibrations per hour with a 72-hour power reserve and manual winding capability. The stainless steel case with super-hard coating is the slimmest of any Seiko 6R model, flowing seamlessly into the multi-row bracelet, with a curved sapphire crystal, screwdown crown and caseback, and 200-meter water resistance.