This is a sword by Goro Nyudo Masamune (c. 1264-1343), considered to be the greatest swordsmith in Japanese history. His swords have a recognizable set of characteristics, one of the most famous being his skill in producing a quality called “nie” an appearance in the blade of Martensite (hard steel in crystal formation) embedded in pearlite matrices that were compared to the shimmering of stars at night.
