特別重要刀剣 Tokubetsu Juyou Touken / Special Important Sword 

What is Tokubetsu Juyou Touken in Japanese Katana terminology?

This refers to a sword that has been appraised by the Japanese Art Sword Preservation Association and recognized as particularly excellent and well-preserved among the important swords. Among the important swords, those that are superior in preservation condition, have a special finish, and are considered equivalent to those positioned at the top of the important artworks designated by the country.