Rivkin

I would argue its late Muromachi Jumyo or possibly Kanemoto. Shinto would have sugu boshi. First generations would have more nie, more complicated work, possibly sugu boshi. I don't see periodic groups of three, not a single one strictly periodic, strictly group of three. I see very periodic gunome-togari with a few sticking out. Its Mino, its possible Kanemoto but unless there is an argument missing, I would personally prefer Jumyo. Probably by a significant margin.

Very late carving, the small details like completely flat toes and foot indicating... nothing good. Don't want to speculate if its cast and finished, but its just late.

Takes a while to get the light source angle right, but that's the key.

Congrats on nice purchase. Here is my take on Kunimitsu. Yes, the site overcompresses.

Here is the item: https://japanesesword.net/products/tanto-kunikane-nbthk-kicho-certificate-shirasaya-koshirae-ubu-nakago-shinto-era-kanagawa-53159?srsltid=AfmBOorUYpeV4tSRMwEZgXoEtofMmWWdLYfGIYOeGbteF2FYgUEst2Ny With such photographs it might be actually earlier than shinshinto, jigane looks correct, also some of the nakago "roughness" might have been photography-related. It can be real Kunikane, post 1670 probably.

Hamon looks like late Muromachi Mino, Bizen or Kaga. I personally would lean a little bit towards Bizen. It is possible it has utsuri which is still visible in these photos.

Jeesh, you beat me at my seven. Photographed only two though.

This is koto, and possibly Bizen or Bizen like.., Something more specific is hard to say in this condition and such pictures.

Decent late Meiji to Taisho or early Showa, for export production, "ken".

That's reasonably common. "Classic" Go has not many options except go down to Tametsugu and the upgrade is probably Masamune. For Shizu it does not have togari, there is slight chance to go Sadamune, you can't go Yukimitsu because hamon is too uneven, Hasebe would typically be rather different jigane. I do dislike dealers. They always write as if they've been family friends with most of the smiths, forcing them to keep in mind when Go's birthday is, and what did Masamune give him the last time everyone been drinking together. That rascal. They don't write "the earliest mentioning of Go is in X", "his birthday is first mentioned in Y". Go, Sadamune, Yukimitsu and Norishige do have arch-typical different clusters; as a pure personal guess in terms of width of the hamon, which continuously increases with time in Soshu until hitatsura and Hasebe, Go is beyond Yukimitsu and at least in Sadamune's timeframe, but before Hasebe. His works are unusually compact timewise, but this might be relative because many others are unusually wide - Tametsugu, Yukimitsu, even Norishige. Then again, nobody in Soshu was satisfied doing just the arch-typical, there are also many works that don't stick anywhere in particular and the early texts that everyone cites with respect to Masamune, somehow dismissing the fact they provide many names which disappeared from our mind because there are no signed examples... well, its not like there are many in Soshu overall.

The only early Soshu smith I personally would be exceptionally careful with is Masamune. There is a significant body of later 1360+ works which can move one way or another, but for earlier blades there is considerably better certainty, Sadamune, Yukimitsu, Norishige all having very arch-typical core body of work, so while there are "on the fence" examples, its not too great a problem. Go is also a relatively well defined cluster. Great (itame/ko mokume) jigane as most of the early Soshu, or possibly something more Yamato looking with masame; clear bright nioiguchi, wide and widening aperiodic notare filled with nie particles throughout. You would not see such width or widening in Yukimitsu, Sadamune tends to be a bit more periodic, the areas where hamon widens are more wave like. Sadamune jigane is probably superior. There are signatures in oshigata, but its an open question.

It is a [potentially] a considerably valuable sword and personally I would investigate the possibility of getting NBTHK papers.

I am not a specialist on this lineage, but what concerns me: - its indeed shinshinto yasurime. - nakago finish is different than typical for Kunikane, though such shape in general is possible, it is much more sharp-abrupt than expected. - nijimei is not too common in shinshinto, with better lineages. - we don't see much in terms of activity, is there something like Kunikane - remains to be seen. I would be a bit careful with this one.

Pure guesses, but: It is [very] late Muromachi. Could be Bizen. Its strange when a few kanji survive like this, the rest disappear. It might be associated with some extreme impact on nakago. It has quite a few ware, which would be a significant detriment for Bizen.

5x more effort into photography and it will be possible to tell.