nulldevice

That book is the Japanese (Original) version of "The Connoisseur's Book of Japanese Swords (刀剣鑑定読本) by Kokan Nagayama. Its English translation is one of the most common books for sword collecting and comes highly recommended here.

You are correct the TH papers state den Hasebe Kuninobu and not Kunishige. I think that blunder with Aoi should be corrected but you did your due diligence and found the misattribution. There are 3 Mumei Hasebe Kuninobu in that database, 2 with den attributions and 1 TH with a direct attribution to Kuninobu. The 2 den Kuninobu are both Juyo daito, and the first makes mention of Kunishige and says: "Kuninobu is said to have been either the younger or older brother of Kunishige, and many works show the style of Hasebe Kuninobu. Among his works, suguha pieces can also be seen, and three signed tachi are extant." I believe this comment about 3 tachi being extant is now outdated as this came from Juyo 20 and there is another zaimei tachi from Juyo 21, and 1 other Tokubetsu Hozon zaimei tachi listed as well. I suppose the 3 that were being discussed in this explanation are the JuBi Tachi, the one in Shizutani Jinja, and another Juyo/TJ blade from Juyo 16. (Thanks to Jussi again for the data here!) The Juyo 43 den Kuninobu says the following: "This is an ō-suriage mumei katana attributed to Hasebe Kuninobu. The Kyoto Hasebe school is considered a hitatsura group contemporary with Sōshū Kunishige and Akihiro, and Kuninobu is the representative figure. Kuninobu is known for his characteristic hamon composed of notare and gunome with yahazu (arrow-notch) tendencies. Suguha works are also seen among his pieces. In most cases, the Hasebe school shows a foundation of notare mixed with gunome and yahazu elements, displaying a gorgeous Sōshū style. This katana prominently displays these characteristics. The form is also typical of the Northern Court period, around the Enbun (延文, 1356-1361) and Jōji (貞治, 1362-1368) eras, making the attribution to Hasebe Kuninobu most appropriate." There is 1 other TH Mumei Hasebe Kuninobu listed in the database, but being TH, there is no more context on it.

Do you have pictures of the books in question?

I find this explanation of a Tokubetsu Juyo (Den Masamune) appropriate and fitting with the explanation by Hoshi and images above:

The blade looks to be signed Tsuda Echizen no Kami Sukehiro. A Shinto smith who signed in this grass style script. He’s also a Sai-Jo Saku smith so the likelihood of gimei is very very high.

There are still useful and incredible uses of AI, even within niche hobbies. That being said, most content now days that is being AI-generated isn't done with educational or research purposes in mind. Its a way to blast the internet with content to drive up engagement, SEO ratings, and other general bloat while adding net negative to the information we have and wasting an enormous amount of energy, resources, and space to fill the web with useless nonsense. On the other hand, there are plenty of situations where the pattern recognition, pseudo-logical processing (the best kind because we can still give it rules to follow but it has "intuition" which allows much more complex pattern matching than one could write in a standard program), and the ability to be constrained allow it to be a phenomenal tool in the right hands with the right intents.

Hallucinations are a fascinating part of generative AI and one that can quickly lead down paths of nonsense if one is not careful. In a world of specialized terminology and weird habits (nihonto is very guilty of this), this becomes even more common. The resources from which ChatGPT or whatever model you were using no doubt are referencing other AI generated articles rife with their own hallucinations. We're starting to see AI-generated "educational" articles pop up with references to nihonto on non-nihonto (typically repro sword sales) sites with a mish-mash of correct and incorrect information. The problem is is that nobody will check these for historical accuracy and the next batch of AI-generated articles will use these as references and sources of truth when making the next article thus further tainting the pool. I remember in High School when teachers would always tell us "Wikipedia isn't a legitimate source, you must go deeper to the source material, journals, etc. and conduct your research there". The same is only more true today in the internet of generative-AI, only a hundred-fold more so. Due diligence is key and in fact, the old books might be making a comeback as sources of wisdom upon which we can study and learn.

One needs to look no further than shinsa costs to understand why things are postured the way they are with NBTHK papers. Similarly, with swords IDK that any points grading system would change things because already you'll hear things like "That blade's a JINO blade" or "this shinsa session is really strong" where you'll have sub-values assigned to the values of each shinsa depending on who the judges were, what blades passed, and what the competition for that year was like. For example how do you grade a newly found, newly discovered for the first time ever Rai Kuniyoshi that is deemed shoshin? Is it an auto 9.8 gem mint because its the only existent blade of this smith and a huge historical discovery for the Rai school roots? What if its a little tired but signed? Still a 9.8? I don't know that the NBTHK could provide some level of objective criteria on which all blades could be judged unanimously. There is nuance within traditions, within schools, and within smiths individually and as more blades are submitted and discovered, the scale on which we must grade all future discoveries also changes. Hence the bucket approach naturally also fits (if not for the income for the NBTHK with the bucket system)

A quick note on the Rai Kunimitsu. The Christie's blade was a JuBi Kunimitsu and not just a Juyo Rai Kunimitsu. There are 23 Juyo Bijutsuhin Rai Kunimitsu and almost 200 Juyo Rai Kunimitsu blades (and counting) currently. There won't be more JuBi Kunimitsu blades. Also, comparing various works of the same smith, one might come across a 10x in value or more at the extremes. An obvious example of this could be a smith who has only a small handful of Juyo or TJ blades to his name and the vast majority sit comfortably forever in Hozon and Tokubetsu Hozon. One might expect that those rare examples of the Juyo or TJ blades will go for much more than other blades of the same smith forever stuck at Tokubetsu Hozon. At DTI this year, I counted over 7 Shizu blades. Most sat comfortably around the 7-9M JPY range with one caressing the 11M JPY range. Same Juyo papers, different shinsa sessions, but the same attribution nonetheless. However, as I looked at each one, there were clear "winners" and "losers" in my opinion as to which ones I enjoyed more and were "worth" more. I say that as an enthusiastic collector and not as a professional appraiser. Consequently the blade that had the healthiest form, minimal flaws, and best polish (in my opinion) was the 11M example. Maybe that's a "pricing bias" or maybe I was actually holding the objectively "better" blade. As a final note, comparing sales across a maker can definitely give us a trend for what a rough value for a certain swordsmith's work might be worth but it is not definitive and each blade must be treated individually when assessing is quality. If we find a blade by a maker and the quality is judged as excellent, then we can assume the value will be, on average, in the upper deviations of the bell curve of prices for that smith. That is, assuming you can rightly assess the sword in hand and judge its quality compared to the swords that have sold for higher amounts in previous markets. I can't do this on the fly and certainly not without time to research on my laptop.

士魂 矢田明督之作 Shigon Akisuke. Someone else can probably chime in with more info about the smith. Edit: Here is the nihontoclub link to AKI29: https://nihontoclub.com/smiths/AKI29

This isn't a real Japanese blade sorry

I believe it’s the Nagamitsu line of Kanemitsu smiths that this Mei is purporting to be. I agree that the hada looks like it’s been “enhanced” and not in a good way. There were many generations of smiths signing Kanemitsu and many signed Bishu Osafune Kanemitsu.

What's your conclusion and why?

A fun little exercise I did using @Jussi Ekholm's wonderful data he's provided to the forum. The filter here is just looking at Juyo blades (Not TJ or above, but I could add that in easily enough), and the first numeric column is the number of Mumei blades and the 2nd numeric column are non_mumei. In the case of the Enju/Enju combo this includes 5 instances where there is a shumei, kinpun mei, or kinzogan mei simply to Enju. The columns in order are: School/Tradition, Smith, # mumei, # non_mumei. Enju Enju 86 5 Enju Kunifusa 0 1 Enju Kunimoto 0 1 Enju Kunimura 5 3 Enju Kuninobu 2 5 Enju Kunishige 0 3 Enju Kunisuke 3 11 Enju Kunitoki 9 23 Enju Kunitsuna 0 2 Enju Kuniyasu 4 8 Enju Kuniyoshi 2 17 There are still some fringe cases that I'm working out the bugs with where the count may be off 1 or 2, but this was a quick bit of tinkering. Edit: I did more tinkering and here's a big table with most of the possibilities of mei realized: Again, a huge shout out to Jussi for the compilation work he's done. I can't possibly say enough about how insightful it has been for me as a data nerd to pour over different possibilities and arrangements of the data he's collected and given to members of this forum. Its truly invaluable and selfless of him for giving this to the NMB community!

I’d suggest doing a little bit of digging on your own and asking yourself whether you think it’s legitimate or not and post your reasoning here before asking for other’s input. Hizento are among some of the most documented works out there and finding comparable examples is easily done.