Four ranks of Nihonto certificate
The NBTHK (Nihon Bijutsu Token Hozon Kyokai), the Society for the Preservation of the Japan Art Sword, founded in 1948, is a highly trusted organization that is sponsored by Japanese government. The organization is responsible for screening and certifying onto Japanese swords. When a sword or fitting is submitted for a “shinsa” (judging), the organization reviews and then issues a certificate with a rank they placed on the piece.
There are 4 ranks. From the highest rank:
The current appraisal system has begun since 1982. "The rank" can help to decide the price of Nihonto. However, there are other factors that confirm the value of it. In fact, the appraisal system applies only to Nihonto made by the swordsmith who had already lived in history.