Hi, I'm surely one of the least experienced person on this forum in relation to Nihonto. The good news is, recently while travelling in Japan I became a first time custodian of two Nihonto, one of which was signed Yamato Daijo Fujiwara Masanori. Also appraised as Tokobetsu Hozon.
I've spent the past few weeks researching Yamato Daijo Fujiwara Masanori.
I can share my findings.
There were two smiths who signed Yamato Daijo Fujiwara Masanori in Echizen province 1600's.
The first generation Masanori. (referred to as shodai)
And the second generation Masanori. (Second generation referred to Nidai)
In the book named, Japanese Sword Smith directory, Japanese edition (which is in English) by Mishina Kenji, I've found the following information (photos attached. Reference: Ma - 121 rank C)
You can also investigate the province Shodai Masanori worked in to find who was the Daimyo of Fukui domain during this period. This timeline is very close to the battle of Sekigahara which marks the beginning of the Tokugawa Shogunate.
Daimyo of Fukui domain in Echizen province 1601/1607 - Yūki Hideyasu
(Seond son of the first Tokugawa Shogun, Tokugawa Ieyasu)
https://en.m.wikipedia.org/wiki/Yūki_Hideyasu
Succeeding Yūki Hideyasu was his eldest son, Matsudaira Tadanao.
Daimyo of Fukui domain in Echizen province 1607 - 1622
https://en.m.wikiped...i/Matsudaira_Tadanao
As referenced, Tadanao was banished and replaced by his younger brother and second son of Yūki Hideyasu;
Matsudaira Tadamasa
Daimyo of Fukui domain in Echizen province 1623 - 1645
https://en.m.wikiped.../Matsudaira_Tadamasa
If your katana is first generation Masanori, The probabilities are it was forged during the reign of one of the above Daimyo.
What historical battles may have Shodai Masanori katana possibly seen?
If it was forged early enough, The siege of Osaka 1614 to 1615.
https://en.m.wikiped.../wiki/Siege_of_Osaka
Samurai of Fukui, Echizen province were sent to Siege of Osaka under the Daimyo Matsudaira Tadanao.
Some additional research can begin from other names referenced in the photos such as;
Sanjo Yoshinori, which Masanori is referenced as being a descendant (I lack further information for now)
The smith he apprenticed under; Kanenori. I'm guessing, of Fukui, Echizen Domain early 1600s
And other references Ive read saying he was the son of a Norimitsu (again, lack further information)
This is all I've found so far. When you come across further information, I would also love to hear.
Cheers,
Ben