Grand seiko watch mechanical gmt this grand seiko watch is a mechanical gmt instrument it comes equipped with 9s66 calibre that performs 28 800 vibrations per hour and has 27 bearing jewels one of its most intriguing characteristics is the mechanical automatic drive system that comes with hand winding capability a 72 hour power reserve is available the watch is protected from water penetration and magnetic fields a special arrow hand indicates the second time zone the dial features a date