The Grand Seiko Automatic Hi-Beat 36000 Professional 600 m Diver's SBGH257 is the limited edition sibling of the SBGH255. It was introduced in 2017, when Grand Seiko became a brand of its own rather than a collection within the larger Seiko family. It features a Zaratsu-polished titanium case with a diameter of 46.9mm and a blue dial.