Tanto from 13th century needs identification

This sword was given to me by my father. It was first handed down to him by his father who was a Lt. Colonel in the U. S. Army and commander in charge of all land and air transportation throughout Japan. For his great help and efforts after WWII, a high-ranking Japanese officer presented him this tanto as a gift. It was said to be from a famous sword maker from the 13th century. It was once identified and certified, yet the papers were lost with my grandfather. I was hoping someone could help me identify it once again, so I may display it with its full honors.

Thank you all!


Sadayuki?

Hi Thomas,

I think the signature reads:

定行
Sadayuki

If that's correct, I don't know any smith called sadayuki from 13th century. There were few in 14-16th centuries though: Sa Sadayuki, Sadayuki etc.

I was only able to find examples of signatures for Sa Sadayuki, but they differ from your sword.

Regards,
Stan

Stan, Thanks so much for the

Stan,

Thanks so much for the translation! Does the rust on the tang coincide with the time period?

Nakago patina looks too young

Nakago patina looks too young for early koto, looks at least late koto. So maybe 16th century, I doubt it's much earlier, could be later.

Yes, Gabriel, I would

Yes, Gabriel, I would agree.

Stan