I was discussing recently about Ikkansai Kunimori with Chris Bowen. Here is what he believes:
"Well, here is my take on this matter...
1. It is well known that Miyaguchi's Kunimori signed blades are made of Western steel. This is noted in period literature such as in Fujishiro's Shinto Hen, a long respected reference.
2. I have been told directly by Miyaguchi's son, who became a respected smith, that Mizukoshi Mitsuhiro, a former student of Miyaguchi, produced these Kunimori (Protect the Country) blades as part of a business venture to meet the demand for swords at the time as well as a way to help his student establish himself financially. The son was explict- Mizukoshi made the blades, Miyaguchi received them in bundles and he signed them one after another while his son held them down, as is customary. You can't get more compelling evidence.
3. As for the NBTHK, their focus has always been on older swords. They would rarely if ever paper WWII era blades until rather recently. When I first moved to Japan, I would ask them all sorts of questions about WWII smiths and sword making and they almost always referred me elsewhere because they did not know the answers to my questions. I have spoken with several NBTHK shinsa team members over the years and they freely admitted that these swords are, in their words, a "blind spot". People who haven't been behind the curtain live with this fantasy that the NBTHK is some sort of sword omniscient monolith that knows everything and is never in error. The truth is it's just a group of people doing their jobs as best they can as in any quasi-governmental agency. They don't know everything and they are not always right. In the later years before I left Japan, when WWII swords started to become a thing, they would actually refer questions about WWII swords to me!
4. As always, refer to the blades themselves. I have seen dozens of the these Kunimori mei blades. Well made they are, but they have all looked oil quenched.
Many years ago I stated that star stamped blades were traditionally made. People who have never been to Japan, can't speak or read the language, have never spent as much as a single minute talking with WWII smiths and people with direct first hand knowledge, who wouldn't know an oil quenched blade from one quenched in water, came out and challenged my statements. Oh, the NBTHK would never paper a stamped blade, regardless they claimed, until l submitted a star stamped blade and it passed as Hozon. They wouldn't accept the WWII army documents, the literature citing, etc.
This looks and smells like the same thing: people with little to no knowledge who have done zero real research blindly claiming that if the NBTHK papered something, it must be the real deal. This is what is known as an "appeal to authority" (argumentum ad verecundiam), It's a fallacious argument used to support an opinion when one has no real evidence.
Bruno, I have done my homework, I am very comfortable with the results of the thousands of hours I have spent with WWII smiths, period Japanese literature, etc. I really don't put any stock at all in what people with nothing but blind faith believe. Everyone is entitled to their opinions and you can't always convince everyone. There are still people who believe the Earth is flat, after all....
mistake corrected - the smith who made these blades was Mizukoshi Hiromitsu. I typed it backwards. Maybe you can edit your post. These blades were made by Mizukoshi, not at the Okura Tanrenjo, but in Mishima, Shizuoka, were I lived for 13 years! They are, at best, daisaku regardless of construction and for that reason alone aren't considered on the same level as Miyaguchi's own work. Western steel is normally not water hardening- it cracks too easily. When quenched in oil, it does not produce significant, if any, nie. This is usually the giveaway. If forged/folded, they can certainly have hada, and oil quenching produces a nioiguchi specifically. These are not dis qualifiers in any sense! Western steel was used because it was easier to get than tamahagane, cheaper, and easier to work with. It was quenched in oil which results in less cracking than tamahagane in water. It allowed smiths to make swords faster, easier, and more cheaply. Exactly what the war effort demanded. And by the way, one shouldn't take the term "Western steel" literally- it simply means steel made using western, not traditional Japanese (tatara) methods.