The mei is unusual:
銘有之 I have never seen this combination before. I don't know if it is alluding to a mei that was once on the sword, or something else.
楊 Another term that is new to me.
I wonder about the two names. Is it supposed to mean that the sword was originally signed by Kanenobu, but was shortened by Nobukuni Yoshimasa? If so, it is written in a way that I have never seen before, but that in itself doesn't mean much. Still, too many novelties make me suspicious, so I don't quite know what to make of this one. Maybe pictures of the blade itself might help.
Many Mino smiths had 兼 in their names, and sanbonsugi is a hallmark of Mino smiths, so...that is something.
Edit: I think the kanji I marked in red is wrong. I think it actually is 揚 (hand radical instead of tree radical)