SteveM

No, the picture is good and clear. It's my poor inability to decipher seal script (and, not understanding Chinese writing conventions). Well, 2nd from the bottom on the right side is 楽, but that doesn't help much. The zodiac year would correspond to 1918 (or another 60-year interval year, like 1978, etc.).

Looks Chinese. Left side is a zodiac date (戊午) and then some numbers after that? But I can't make it out.

Hello Steve, The smith/signature is the same one as in this thread below.

Yes, that is correct. Not imperial. It's a gift for a boy on his becoming 3 years of age (given on Boy's Day, May 5th, 1916). The boy's surname is Matsuba. Not sure if the rest is his given name, or if it is 満礼三 (in celebration of 3 years).

I'm sure the red "hozon" seal on the tag means that bottom tsuba received the Hozon (or "worthy of preservation") appraisal, and comes with that authentication paper. So yes it looks like an authenticated Sōten piece, as Dale says (hence, the elevated price). I also agree with his thoughts on the top tsuba (the one for 33,000). The theme might be the sages Kanzan and Jittoku. Authentic Japanese antique, probably from the 1800s. Another view and explanation of this theme. https://www.metmuseum.org/art/collection/search/25684

Nice helmet. Great photos, too.

I agree with Chandler - if you are in Okinawa it will be relatively easy to send it to the NBTHK for authentication. It is still a slightly cumbersome process, but at least you will be doing it from within Japan, where the postal system is excellent, and the fear of the sword getting hung up at customs, or hit with an arbitrary import duty, is virtually nil. (I'm assuming you are not sending it from a US military base). If you want the help of an English-speaking agent who can get it to and from the NBTHK, you might contact Robert Hughes at Keichōdō. He's a sword and armor dealer, and long time resident of Japan, and he helps people get their swords authenticated. There is enough in the mei and the file marks of the nakago on your sword to pique interest, but it will be difficult for any of us to authenticate. You will get some good guesses, but ultimately you will want the judgment of an expert panel who can examine it in hand. Actually its the sword itself that needs close examination rather than the mei (or, rather than just the mei). The sword needs to match the sword-making style of known/authenticated Masashige swords. Slight variations in the signature might be tolerated if the sword looks exactly like a typical Masashige sword should look (steel grain, hamon pattern, etc.). The broad features can be seen in photos, but often its difficult to pick out the very fine details, and these details are usually important.

Nippon/Nihon damashii is correct. And I think your intuition is correct: the words may indeed have been inscribed to partially obscure the Shōwa stamp. Katō Jumyō kore wo tsukuru would be the proper kanbun reading, but nowadays everyone just abbreviates it, word-for-word: Katō Jumyō kore saku.

Same sword as the one in this thread

Looks like Tenshō (天正). 1573-1592.

Yes, this is correct. I would say the reading is: Ishii-ke mamorigatana

The squares in the diamond shape is called "maru ni yotsume-hishi", used by numerous families. https://myoji-kamon.net/kamonDetail.htm?from=rank&kamonName=丸に四つ目菱 The "yin-yang" symbol is also a family crest (hidari-futatsu tomoe). https://irohakamon.com/kamon/tomoe/hidarifutatsutomoe.html The round, indistinct remains of a seal may be "maru ni mitsuhiki-ryō", also used by many families. https://irohakamon.com/kamon/hikiryou/marunimitsuhiki.html As for the meaning; they could be crests representing a joining of families, or an alliance of some sort. And of course you can't discount the possibility that the item was made in the late 1800s to appeal to foreign tourists. I'm probably inclined to think the latter. Quite flashy, not suitable for the battlefield, not suitable for official business - so probably something made for some non-samurai with a bit of money, or made for the foreign tourist trade.

As a start, here is the website of a swordsmith who takes orders, allows on-site visits, and has some information in English. https://www.hiratatantoujou.com/

會津藤四郎 Aizu Fujishirō

Yours is signed Morikawa Teruhisa (森川英久). There is no Morikawa Teruhisa listed in Wakayama's directory. There was a Teruhisa who studied under Ōmori Teruhide, but according to Wakayama he never used the "Morikawa" name. So...an unknown smith, or a name that is intended to deceive?