Thank you so much for your replies.
If you look closely, you can see that a signature has been removed. I think it's a sword from the Edo period. I find the story behind it very interesting. Unfortunately, I can't seem to make the old signature legible anymore. Perhaps I should try taking a picture with a flash.
Of course, I would have been happier if it had been an original Yasutsuna sword.
Thank you, Jean and Ray.
Best regards, Raphael