国宝 Kokuhou / National Treasure 

What is Kokuhou in Japanese Katana terminology?

According to the Cultural Property Protection Law, among the important cultural properties designated by the country, those that are of high value from the perspective of world culture and are unparalleled treasures of the nation are designated by the country (Minister of Education, Culture, Sports, Science and Technology) (Article 27, Paragraph 2 of the Cultural Property Protection Law). Designations include buildings, paintings, sculptures, crafts, calligraphy and books, old documents, archaeological materials, and historical materials.
(The division of National Treasures and Important Cultural Properties is as described above, and since weapons such as swords and armor are designated by the Agency for Cultural Affairs under the category of crafts, this description has been made.)