This is the sword's registration certificate. It doesn't imply authenticity of the signature. In a way, it kind of says "this is an authentic Japanese sword", but even then some weird things slip through the registration system. Your particular registration certificate is dated 1968, and comes from the Kōchi Board of Education. Each prefecture's Board of Education handles the sword registration paperwork for swords in that particular district. Your certificate indicates the sword has the inscription "Azuma Tamonbei Masatsugu", which is the swordsmith's name. He would be a swordsmith from the early-to-mid 1600s.