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I am not following your logic here. Ko-Hoki smiths were in Hoki province on Honshū, not on Kyūshū. And they were active in the Heian era, so well before Norishige was born. In any event, I like your Senjuin. It is a great example that Sōshū den was not the start of vigorous nie hataraki. Relatively, Sōshū den was a late bloomer, and it drew inspiration from some the best traits of many smiths who were active long before.

This is a great resource—thanks to all involved! For those who prefer a book, the Northern California Japanese Sword Club has volume 1 in a reorganized edition: Book on Lulu

Unfortunately, my books all show the much longer mei—nothing with only two kanji. But some of the Onizuka Yoshikuni mei in my books look very similar at least as to the two kanji on your sword and as to their location relative to the shinogi (ridge line). I am now seeing that you posted on NMB about this sword 13 years ago well before its restoration. It is great to see that you followed through with your original plan. Who did the polishing?

Thanks for posting the additional photos @acefighter66. This is a great heirloom. While there are some similarities between the chiseling of the kanji on your sword and some of the examples the polisher provided, only having a two-kanji mei is obviously quite different than the longer signature that the Onizuka Yoshikuni smiths typically used and as shown in the examples. Additional research on the mei is needed. If I have time, I'll see what I can find in my books. To echo what @Geraint, shinsa might be your best option for attribution.

Well, I’m pretty inexperienced with kantei, so I could be way off here. I’m thinking Yamato-den, perhaps Naminohira. It looks like there are some areas of ayasugi hada and I see shirake utsuri.

I like your sword @Zoglet! Thanks for sharing the photos. I am surprised that no one has yet offered a kantei bid.

Thanks for sharing your experience @ZH1980! How was the customs declaration/tariff process once you entered the U.S.?

It was my third year attending the Las Vegas show, and I had a great time. There is something for everyone there--items are at all price ranges. I always enjoy seeing friends and meeting other collectors. While it is still a relatively small show, more tables were occupied than last year. And there were some dealers I had not previously seen at this show, such as Ginza Seiyudo with a really nice Ayanokoji tachi and a couple of nice kabuto. As @Scogg mentioned, Brian Tchernega's presentation was very informative. Mike Yamasaki gave a short behind-the-scenes presentation about his work on Pawn Stars, and there was an entertaining iaijutsu demonstration. The large, adjoining antiques arms show is also worth seeing. Several dealers over there had nihonto, menpo, and kabuto, including a nice kawari kabuto.

There are quite a few familiar faces in this excellent NHK World feature in which @Keichodo has a starring role. View it here.

Great video and explanation for those unfamiliar with nihonto. But as I watched the curator bend the blade, I doubted that the strict prior Japanese curator would have approved.

Anything is possible, but if that is a shill bidder, it would not make much sense for that bidder to be the first bidder on less desireable items that may not draw other bids. Now if the auction closes with only mrtierney50's bid, and the item gets relisted for sale on Aoi's website, then you might have a case to make. Internet auctions can be unpredictable and participant intentions are unknown. We hope that everyone is participating in good faith, but that simply isn't always reality. There are shills, of course. Some people participate with no intention of winning the item--they like being part of the game and drive up the cost without collusion. Some get carried away and bid well more than something is worth due to competitiveness. Yet others win auctions with no intention of paying. All very frustrating to legit, rational bidders.

Having gotten a preview, I can say that @nulldevice’s project is going to be a great resource—especially for visual learners. Adding/correcting the data will be very worthwhile.

@Rhizosphere Depending on your location in the United States, you may want to attend one of the four sword shows around the country to see if you can find something in person. This helps immensely compared to shopping only from photos. The Las Vegas show is coming up in a couple of weeks.

When shipping in the United States, USPS Registered Mail is best for high value items up to $50,000. It is slow but secure, as the package is signed for each time it is handed off internally and it is held in a secured area while waiting for the next leg of the journey. And the insurance is relatively inexpensive. Otherwise, I insure collectible items using a special policy (like this) that covers items in transit, and I ship them UPS Next Day Air to minimize the item they are in the UPS system.

I cannot speak to the legitimacy of the signature, but it reads Sagami no Kuni Tsunahiro. There are many generations of Sōshū Tsunahiro smiths.