Rivkin

Almost certainly recent, like WW2 era.

Yep, border of Muromachi and shinto. Could be many things, like shitahara.

I would even go shinshinto, but hard to be certain.

I did not check any references myself, but with Senjuin unknown signatures are quite common. They did not have Edo period's genealogies to back them up, being an outsider group in a sense, while at the same time they are really old, with late Heian swords found here and there. So what would be a slam dank TJ with Bizen or Yamashiro becomes just a guaranteed TH with Senjuin, with not a lot of extra money from the fact that its signed. Funny how a low grade ko Hoki will set you back easily 3 mil yen, while very good Senjuin can be had for under 2.

Its almost certainly not koto, therefore Yamato attribution can be difficult.

The curvature is in the center, chu kissaki... Either the very end of Kamakura, or between 1570 and 1640. Statistically 1,000 times more likely to be the latter.

Judging from hada alone this is something relatively modern, no earlier than shinto, and quite possibly much more recent. There was a movement within shinshinto (Ikkansai and others), who experimented a lot with very high contrast hadas which they could heat treat only at very low temperatures, so you see almost no transition between hada and hamon, while the structure is quite vivid.

At the risk of starting a heresy: jigane has a strong Muromachi feel to it. Kaga Ietsugu is likely one of the least faked smiths out there. Some very early works are decent, but overall its a typical Muromachi period mass production which imitates the works of better known schools. Even without papers I personally by default would treat such blade strictly as shoshin. Even if its not an exact match to photographs on the internet, as long as the general stylistics - signature location, how deep and long are strikes etc. is a general match for the school.

Best wishes, its very interesting. Any star blades - I think I am not alone in now wondering whether one should get a ticket to the east coast.

Kozuka looks high end. Can be Yoshioka. The blade is almost straight, very beefy, some taper... Maybe Kambun shinto. The nakago and the boshi are too most important elements to be more precise in attribution.

Its Bizen Ichimonji style. Kissaki proportions at the very least are not Kamakura, as is shape. There are "crab claws". There a big of fumbari here, but can be distortion from wide angle lens. I think, either Ishido from around 1640 or late Muromachi ...mitsu or Naotane in his Muromachi Bizen style. Boshi would be extremely useful to be more precise. I suspect Ishido, but I always say that. Got burned too many times on those Ichimonjis.

I don't think anybody issues papers to Hosho Sadamune anymore for the last 40 years. The light source is very non-uniform, but besides that I don't see anything super-criminal... On the second blade: there were Yamashiro smiths signing above the ana and towards the mune, though if there is just one ana it tends to be then considerably lower than the signature. By default I would suspect gimei here.

Well, if it were up to me a major sword show would have to have a kantei contest. Two rounds - first something very basic, second with interesting blades. Token fee to participate. With (electronic) publication of the catalogue with quality photographs and discussion of kantei points. It would also include a few select blades awarded "best in show" from the dealers present at the show. Unfortunately, knowing American community I expect they will spend more time devising who is going to be the Lord President of Nihon Bijutsu Kantei Committee and who is just The Grand Marshall of Editing and Publications.

Very Personally: I usually don't partake in kantei like this, because the answer in 95% cases is hidden within the text of the task. You have to learn for which blades the writer points out to mokume or "very dense hada" or some specific term related to utsuri or boshi etc. This can immediately put you very close to the right answer and then you look at oshigata to see if the length of kaeri etc. etc. closely matches any particular name. The good thing it trains one to consider such "small" traits in situ. At the expense of learning in detail how this particular group uses the language and what do they emphasize in oshigata. The bad thing is translating from this to real blades can be difficult, and one can be very dogmatic rather than pragmatic (or probability-driven) in his appraisal. For example, kyo-saka-ashi is something one encounters very commonly in kantei exercises even when working with real blades, provided the organizer has access to the ones that exemplify the style in every detail. And then in real life you are hit with Aoe blade that has it next to Rai blade which sort of does not.

That's usually done for suriage blades when there is a solid chance of pre-Muromachi attribution. TH Tegai then with non-Nambokucho sugata would imply Kamakura date, for example.

Let me be a REALLY bad person here: 600-1000$ depending on transport options spent to replace completely satisfactory judgements assigned to mid-grade items. Just so that the "experts" don't laugh at you for having green papers. Based on kicho papers, the sugata is most likely from the very end of Muromachi but not the o-kissaki type or something else which would hint towards Nambokucho possibilities. It has some Soshu flavor, nie based wide hamon. Shitahara hints towards active mokume. Even without seeing the sword, but out of sheer arrogance: So it can't be Kamakura Soshu, can't be Nambokucho Soshu... For late Muromachi or even early Shinto suriage work like that there are myriad options, all more or less valid. You can then submit it to both NTHK and you will get another two, different judgements, but from the same period and roughly the same level of smith. Its not like "Shitahara" ko-waki which can easily jump to late Nambokucho Soshu. Or O-Kissaki Soshu blade judged to Tsunahiro, which can if kasane is thin enough move all the way to Hasebe.

There are signed Sueyuki, typically they are offered in 10mil yen price range though. To me Sadatoshi attribution denotes Heian to mid Kamakura sugata and Seuyuki is accordingly mid to end (1250-1310) period. In both cases the craft is very antiquated with minimal trace of influences as established by Rai Kuniyuki and other more fashionable school. Obviously condition issues are such that even well preserved work will have somewhat non-uniform jigane, but: The jigane is in general weaker compared to Kuniyuki, the ji nie is less distinctive, the color is noticably whiter and hazier. As in Sanjo work, hamon is ko nie based, there can be prominent masame close to ha producing hotsure/uchinoke and tobiyaki tend to line up with masame lines. There can be rather rough ara nie, though hamon's nie size is very well controlled. Nioiguchi is quite bright, though in books its other qualities tend to be emphasized more. Yakiba can be a strange (antiquated) mixture of ko choji, togari and almost Yamato looking "belts" of nie. Utsuri like in this work can be quite prominent, but its not as clearly defined as in later works (midare? jifu?). Boshi has prominent hakkikake but is rather thin when it begins. I considered waiting a bit more, but I felt bad about people going into completely different directions, maybe in part relying on my answer to Enju quess.

For some reason attributing Muromachi blades specifically to Akihiro was a common thing in Edo period. I had quite a few Honami attributions like that. Go figure.

Late Muromachi 1520- waki, maybe in Soshu or Seki, Sengo or other related style (nakago will tell more). Today Muromachi attributions to Akihiro are not supported, though for earlier Muromachi periods they are not outright rejected.

Even with non-informative photos. I feel a bit strange about this one.

Quite a few of the blades mentioned I would take for Nambokucho, like this one: https://nihontou.jp/choice03/toukenkobugu/katana/1084/00.html Longer kissaki, flatter curvature... The seller is being aggressive in the description.

Late Kamakura blades do not have a reputation for being confused with other periods. There are some Rai or Yamato works that were quite well replicated or imitated in early Muromachi sugata included, but that's about it. The danger zone is something like Soshu from 1360-1380s. There is like a stack of papers oscillating between "Shimada" and far more seldom "Uda" and Nobukuni, Etchu Tametsugu and first generation Soshu Masahiro.

There is two order magnitude difference between the commonality of late kamakura blades (i.e. post-Mongol): Tegai, Rai Kunitoshi etc. and early Kamakura blades (ko Bizen, Rai Kuniyuki etc.). Late Kamakura does have a hard reset at 1330x when sugata changed.

I am definitely the last person to be relied upon for proper understanding of the terminology and rules, but: the blade is Ayanokoji, Kamakura. In most tables this is dozen to things like Munechika and maybe something like Rai Kuniyuki. With Enju I had to look up the tables, and (I hope I got this one correctly) some books like Conneusiers... placed Enju as tori yoku for Ayanakoji. Rai would be dozen for Enju.

With a different, i.e. Kamakura shape here. Hoping not to sound too professorial, but that's what the earliest pieces look like - Yamato, Soshu, Bizen (ko choji) all in one piece.