Kiipu

The sword was refitted during the 1944 to 1945 time period for military purposes. The 昭 stamp is clearly visible and thus accounts for the second mekugi ana (tang hole). 関佐光信光作 Seki Sakō Nobumitsu saku. This sword is a textbook example of what is discussed in the article below. Note the poorly cast brass crossguard, the non-pierced iron? kabutogane. As indicated, it would have had a leather combat cover over the scabbard. I think the sword is worth the asking price. The Atsuta Factory & Military Swords

Just one more thing, the katakana characters are following the order of the Iroha poem. Japanese mllitaria collectors frequently refer to them by the number and not the sound. 1.　イ　I. 2.　ロ　RO. 3.　ハ　HA. 4.　ニ　NI. Iroha

It is the katakana character ニ which is pronounced as "NI". It is used as a prefix to the serial number. ニ 三七五 NI-375. When time permits, can you post pictures of both sides of the tang and one overall picture of the sword with scabbard placed below the blade? For starters, take a look at the article below. Mantetsu - South Manchurian Railway

Many thanks for looking Peter. No need to proceed further and risk damage to the habaki. The kabutogane looks to have a deeply struck 東, which would indicate an army contract blade from 1942.

The red paint toward the bottom of the tang is the number 23. The prefix to this number eludes me however. This number is also on the bottom of the hilt. 二三 = 23.

Peter, can you check the date side of the tang, that is the side marked 昭和壬午秋, for any small M stamps. The flattened M stamp will usually be located toward the top, the bottom, or both top & bottom. If on the top, they are sometimes under the habaki.

Type 95 Military Sword made by Suya, serial number 49810. Seems the pictures are now missing from the OP. Fortunately, I had downloaded and saved the pictures for later viewing. Attached are the pictures which have been resized and converted to jpegs.

In the meantime, take a look at this Hiromasa 博正. I wonder if this is another example of a stamp removal? Thoughts anyone? 豫州北條住博正作 昭和十八年二月日

When the dust settles, please post a picture of this side of the tang. Also, can you see the outline of the removed stamp or is it completely obliterated?

I am told by someone more knowledgeable than I am that it is a "navy" helmet and not necessarily a "NLF" helmet. If you have additional questions, I would suggest posting over at the Japanese subforum at WRF. WRF Japanese Militaria

Ran across this a few days ago while reading Dawson's book. The quote is coming from a picture caption and is easily overlooked. Dawson, Jim. Swords of Imperial Japan, 1868–1945. Cyclopedia edition. Stenger-Scott Publishing, 2007. Page 156.

Looks like a name stamped on the crossguard. 高塚 Takatsuka plus other pronunciations. The first name is hard to make out but ends with 崎.

Cross-Reference Theater-made Gunto

That would indicate the WARRIOR stamp was not that of a sword fitting shop then?

"I think" your right! 島田義助作 Shimada Yoshisuke saku. The WARRIOR stamp has also been noted on blades made by Yoshichika 吉近. I think the logo could belong to a either a forge or sword retailer located in Seki. Yoshichika katana with REALLY Odd Stamp in English!

The lineage chart of Hiromasa courtesy of @Stephen. Yoshū Hōjō-jū Hiromasa katana in shingunto koshirae

Below is a link to an early "Star" stamp from the same smith. This particular blade is dated October 1942. Note the different mix of inspection stamps. Mal's tome mentioned above goes into this in more detail. Can anyone translate this?

Hiromasa 博正 was from Ehime Prefecture 愛媛県. The 昭 stamp was only used in Gifu Prefecture. So it would be impossible for it to be that stamp. For more information about Hiromasa and Ehime Prefecture, I would suggest taking a look at the monograph below. Showa Period Swordsmiths of Ehime Prefecture

I did not see it mentioned, so translated the name of the swordsmith. 平田秀光 = Hirata Hidemitsu. A link to one of his blades in a naval mount. Sword in Naval Mounts And another with a mystery anchor stamp. Nakago Stamp

The location you marked is usually where the "Star" stamp was located. If the sword came via Japan in the postwar years, the "Star" stamp could have been removed, so as to register the sword with the authorities. Wartime stamps were frowned upon, including the "Star" stamp.

@Spartancrest

I think the picture is upside down. The right column of kanji characters could be some sort of number? 一ノ一七七 ノ = katakana NO.

I found two other swords by this swordsmith. @Markus Below is the first one. Not much other than the characters. Interpreting kanji on samurai sword The second one is in naval fittings, same as the one in the OP. It is over at auctree, item b1106655914. I will post the link but it will come up forbidden. It has the same style habaki as the OP. https://aucfree.com/m/items/b1106655914

A three part interview of Paul Martin conducted by Shohei Nagatsuji of Japan-Forward.com. Interview

Maybe your thinking of the following stamp(s). Arsenal Stamps.