Dual-signed Type 98 Officer’s Shingunto

[I_Kendo_It]

I recently acquired a Type 98 Shinguntō and have been researching its history, classification, and potential value as a collector’s piece. I’d like to share my findings here, and would greatly appreciate any feedback, feel free to prove these findings wrong with your expertise and experience .

 

I'm fortunate enough to be in touch with a few Nihontō specialists in Japan whom I met while living there. While I am limited to sharing photographs rather than the blade itself, they were kind enough to tell me a lot of things.

Below is the information I’ve gathered from one, (translated from Japanese using AI, so it may sound a bit weird or off):

 

 

『On the tang (nakago) of this blade, one can observe the stamp ‘Shō’. This stamp indicates acceptance by the army during the Shōwa period and is most often found on non-traditional Shōwatō (oil-quenched, made from industrial steel). However, the presence of a stamp does not automatically make a sword a Shōwatō, since the only true criterion is the method of manufacture. Some swords bearing a stamp have passed shinsa and classified as gendaitō.

 

On this blade, kitae-ware appear, signs of folded forging ; and the nioiguchi of the hamon stands out and shows similarity to other niedeki sanbonsugi hamon produced by Ujifusa. These characteristics are typical of blades produced using traditional methods, by water-quenching and folded forging. It is shows similarities to gendaitō No. Tokyo 189513 by the same smith (Ujifusa). It is therefore possible that this sword is a gendaitō, although further examination is required for a definitive answer. Photography may not capture all details, and aged or rough polishing may hide nie, nioi and hada.

 

The tang bears two signatures: ‘Shinoda Ujifusa’ and ‘Kanetomo.’ Ordinarily, a sword carries only a single signature, but when two names are inscribed on the same blade, this generally indicates proof of joint work or a master-disciple collaboration. Here, the signatures on this blade do not appear to have been carved by the smiths themselves, but are meishiriki-mei, that is, inscriptions traced by a professional engraver commissioned for this purpose. At Seki, during the war, such a practice was not rare due to the demands of rapid production; nevertheless, the presence of two mei on a Shinguntō remains very unusual.

 

Shinoda Ujifusa was a prominent smith of Seki during the Shōwa period, an award-winning craftsman of great skill within the Mino tradition. Kanetomo was also active in the same region at that time. The presence of both signatures on this blade suggests a collaborative work, with Ujifusa as the master smith, and Kanetomo in the role of assistant or disciple.』

 

Here is the referenced gendaito : Katana - Ujifusa - Uchigatana Koshirae - Ubu Nakago - Gendai Era - Tok | Tozando Katana Shop

I'll also include some pictures ! He advised me to take pictures with a 45 degrees angle as they reveal the nioi better than straight-on pictures on swords with aged polishing. Here you go ! 

 

1/ Overall pictures

 

 

2/ Nakago details

 

3/ Sho-stamp

 

4/ Hamon details (those pictures are quite hard to take, it's clearer in person... detail gets lost in pictures)

[Mark]

from pictures it looks oil tempered.  has decent military mounts and that is popular now. I would think it would be most valued by a military sword collector.  In my area it would probably sell in the $650-900 range....... just my opinion based on what i see

[Rawa]

I see koshirae alone sells on ebay in 400-500$ range. But yeah paying ~1500$ for it or more is too much.

Can anyne provide Fuller and Gregory 'Swordsmiths of Japan 1926-1945' oshigata 366? It is about this RJT I think.

Dunno about this being oil tempered there are't any darker spots indicating oil.

[I_Kendo_It]

1 hour ago, Rawa said:

I see koshirae alone sells on ebay in 400-500$ range. But yeah paying ~1500$ for it or more is too much.

Can anyne provide Fuller and Gregory 'Swordsmiths of Japan 1926-1945' oshigata 366? It is about this RJT I think.

Dunno about this being oil tempered there are't any darker spots indicating oil.

 

I can confirm that it has no such dark spots, and the person I contacted compared this hamon from the linked Gendaito by Ujifusa (area with two "hill-like shapes" with a thin nioi side by side) :

 

To this same pattern with two small mounts visible here

 

In my case I'm in the European market. I'm not looking to sell, I'm just curious and love to learn about these things.

 

 

[Kiipu]

The subject of traditionally made and guild stamps can get confusing at times.

Sunagashi

[I_Kendo_It]

1 hour ago, Kiipu said:

The subject of traditionally made and guild stamps can get confusing at times.

Sunagashi

Yes, looking more into the difference I've come across this, saying that some gendaito also look like they are oil-quenched, and that even some were first water, and later oil-quenched at Yasukuni... It's a rabbit hole I didn't expect.

 

The gendaito linked in the initial message by Ujifusa also doesn't have a lot of hataraki, nioi or nie, and indeed it's quite similar, so it could be the smith's style... I guess the only way to be truly sure is by scientific testing, or time-travel. Anyway I'm getting confused.  Maybe the NTHK shinpan who give papers are hiding secrets ?

 

[Scogg]

Hello, I_Kendo_It / E.N, 

Interesting sword! 
 

Just a quick reminder, as part of our forum guidelines, we ask that all members sign their posts with at least a first name. It helps keep the community friendly and personal.

https://www.militaria.co.za/nmb/topic/27534-welcome-to-the-forum-please-read-here-first-before-posting/#comment-277750

 

Welcome to the forum, and thanks for sharing your sword with us!

All the best,
-Sam

 

[John C]

8 hours ago, I_Kendo_It said:

the presence of two mei on a Shinguntō remains very unusual

E.N.

Additionally, you will see a polisher's name on a blade sometimes. Just for added info.

 

John C.

[Brian]

With that Sho stamp, you can be almost assured it is not 100% Gendaito. I would bet on oil quenching. That said, it does have hada and I suspect this is a high level Showato that was forged and folded, but something in the process was not 100% traditional and it therefore is probably not considered a Gendaito, but something in between.
Looks like a decent sword, and would probably still paper on a good day. One of those "in between" swords we come across that is high end 'arsenal' made by a smith.

[I_Kendo_It]

15 hours ago, Scogg said:

Just a quick reminder, as part of our forum guidelines, we ask that all members sign their posts with at least a first name. (...)

 

 

Okay thanks ! I wasn't sure if just initials would be fine. It's updated now.

I have two first names. One is very identifiable, so I used the second one.

 

13 hours ago, John C said:

Additionally, you will see a polisher's name on a blade sometimes. Just for added info. (...)

Good to know ! In that case Kanetomo could be the polisher. Thank you.

 

8 hours ago, Brian said:

With that Sho stamp, you can be almost assured it is not 100% Gendaito. I would bet on oil quenching. That said, it does have hada and I suspect this is a high level Showato that was forged and folded (...)

Thanks for the info ! After your message I decided to do some research. If you don't mind let me share my findings.

 

Notably the Ohmura website says this :

Quote

 

"国・県当局に運動して、鋼材から生産する新作日本刀は全部、「関刃物工業組合」の検査を受けさせ、合格品には刀剣の中心(茎)に
「関」の検査刻印を打った。"

 

(After lobbying the national and prefectural authorities, all newly made Japanese swords produced from steel were required to undergo inspection by the Seki Cutlery Manufacturers’ Association, and those that passed had the ‘SEKI’ inspection stamp struck on the tang (nakago) of the blade.)

 

Quote

 

昭和14年頃※から名古屋陸軍造兵廠関分工場が検査印「関」を使用するようになった。※ 推定
その為、内務省令に依る「桜の中に昭」の字を配した検査刻印に変更した。
こうした検査刻印を打たせることで品質を保証させる事に成功し、全刀剣需要の大半を独占するに至った。

 

(Around 1939 (Shōwa 14), the Nagoya Army Arsenal Seki Branch Factory began using the inspection mark ‘SEKI’.
Consequently, the inspection mark was changed to one showing the character ‘Shō’ (昭) inside a cherry blossom, in accordance with Ministry of Home Affairs regulations.
By requiring these inspection marks to be applied, they succeeded in ensuring quality, and eventually came to monopolize the majority of sword demand.)

 

This indicates that the stamps were inspection marks, rather than distinctions of production processes. And that the "sho" stamp proves army inspection, the "seki" stamp proves seki cutlery manufacturer's association inspection. That means that swords carrying these stamps can be made by any production process.

 

However, there's one more nuance to be made. In the first quote, the word "steel" is used (鋼材) as opposed to tamahagane (玉鋼). As such, it is likely these stamps show tamahagane was not used, though I can't confirm this definitely unless we have primary sources of regulations or legislation.

 

As for the classification as "Gendaito" or not :

1/ NTHK : The NTHK appear to base their classification on the technique and authenticity of the signature rather than the material. Hence the NTHK giving papers to stamped Nihonto that are likely not Tamahagane.

 

NTHK papers aren't extremely strick and can attest authenticity (Shinteisho). I had seen examples of "seki" stamped gendaito papered by the NTHK.

 

2/NBTHK : NBTHK is a stricter body and only papers "preservation" swords and "special swords" and above (保存刀剣, 特別保存刀剣). Even so, their rules do not at any point mention tamahagane but rather quality of worksmanship, condition, and historicity, and are significantly stricter on newer swords. (31-3 審査規程第１７条第１項に定める審査基準 27.5.19~.pdf)

 

It even says that "work by living artists are not eligible fur judging" (生存する作家の作品は審査対象外とする。) so I guess tough luck for modern gendaito smiths, they need to literally die to have their swords even be considered. 

 

In fact, the NBTHK even accepts non-tamahagane steel in their sword-making competitions 2025, saying that Tamahagane is preferable but not required. (作刀の部については、日刀保たたらの玉鋼を使用することが望ましい。) 現代刀職展（作刀の部） | 日本美術刀剣保存協会

 

All that seem to show that mill-steel gendaito exist, they can probably get NTHK papers attesting to their authenticity, but not NBTHK papers attesting to their special historical value. These finding seem to meet what the expert I had initially contacted said, that the real standard to determine what is gendaito is production process.

 

In conclusion that this sword could be classified as mill-steel gendaito, if it indeed turns out it's made with mill-steel, forged in the kitae method, and water-quenched. However personally I don't know if it's folded and water-quenched. Of course I'd be happy if it turns out to be of the standard that could get NTHK papers.  

 

[PNSSHOGUN]

The Sho stamp indicates some part of the manufacture was not traditional, I would hesitate at calling this Gendaito and would think more along the lines of higher quality Showato. 

[I_Kendo_It]

1 hour ago, PNSSHOGUN said:

The Sho stamp indicates some part of the manufacture was not traditional, I would hesitate at calling this Gendaito and would think more along the lines of higher quality Showato. 

Thanks !

 

It may be wishful thinking, but here are multiple seki-stamped swords that have passed shinsa and been papered. In practice it seems that those swords are not automatically excluded from being considered "nihonto". 🤔 And given Ohmura indicates that the Sho-stamp and Seki-stamp are basically the same thing : examination stamps guaranteeing a quality threshold can be met ;I feel like my analysis isn't unreasonable.

 

I guess Brian is quite right, saying : "Looks like a decent sword, and would probably still paper on a good day. One of those "in between" swords we come across that is high end 'arsenal' made by a smith."

It's in between, and could also be, like you said, a higher-quality Showato.

[Brian]

Leonidas,
Trust me, in the 19 years that we have existed, there has been a ton of research, including original production instructions and procedures etc etc. on what exactly those stamps mean.
If you search the forum you'll find hundreds of pages about it.
The fact is, over the past few years, it is widely accepted everywhere that the sho and Seki stamp are on blades not fully Gendaito. And by Gendaito we of course mean the collector-assigned meaning, and not the true meaning which is just an era.
To collectors worldwide, a Sho stamp means it is not fully traditionally made. That doesn't mean it can't be a high level forged and folded blade, but something about it isn't fully traditional.
Doesn't really matter how the NTHK or NBTHK regard them, they only really became interested in wartime swords the past few years, and we have already demonstrated that with the right contacts or circumstances, full Showato will sometimes slip through the cracks and get papers. Doesn't change the facts.
This is a nice one though. But I wouldn't call it a Gendaito.

[I_Kendo_It]

Thank you Brian, I do trust your and the forum's experience. I'm just a very inquisitive person with legal and investigation specific training. I hope my questioning comes off politely, the way I mean to. 

 

In any case I'm particularly interested in the original production instructions, procedures you talked about. I'll look into it. The 50 pages on arsenal stamps are daunting. I have advanced up to page 22, and so it's clear Bruce Pennington did a lot of research, and I can't reach a definitive conclusion... Let's keep going ! I also found his booklet, version March 2025 which I'll read.

 

[Brian]

No worries at all.
There is some related info here: https://www.militaria.co.za/nmb/files/file/39-ww2-rikgun-jumei-tosho-documents/

and I am sure people will suggest more. There are other military docs out there somewhere.

 

[Bruce Pennington]

Hi Leonidas!

I'm a little late to the discussion.  You can read about the use of the Showa and large Seki stamps by the Seki Cutlery Manufacturers Association in the beginning pages of my http://Stamps of the Japanese Sword article.  I don't have the direct links to the only two pieces of actual documentation that we have, but when time is available, I'll try to provide them for you.

One comes from the Seki City website, which states that the association was inspecting and stamping "all swords" made in the area, but doesn't state which stamp was used.  The "all swords" makes it sound as if both showato and gendaito blades were stamped.  However, Ohmura has a page depicting a tally of inspected blades by the association, and a side note to the chart states that the total does not include gendaito as "they were not inspected."  So, I suspect the statement in the Seki City website is a generalization and not precise.

 

We also have an article from 1940, found by Nick Komiya at Warrelics, that clearly states the stamp being used by the Cutlery association was the Showa stamp.  Observational evidence in my ongoing stamp survey confirms the Showa stamp was the first to be used, starting in 1935.  Ohmura's statement about the Seki stamp is partially true, in that the association, for an unknown reason, changed over from the Showa stamp to the Seki stamp starting in 1940.  There was an overlap - Showa stamp use: 1935-1942; Seki stamp use: 1940-1945.  The association drastically tapered off the Seki stamp in '43 after the Nagoya arsenal started using the small Seki stamp.

 

Lots of information, but I appreciate your inclination to dig deep and research things.  It's is what I enjoy doing, as well.

[I_Kendo_It]

Thanks, Bruce! I’d be glad to take a look at the documentation.

 

From what I’ve gathered, the Shō stamp was in use between 1935 and 1942. Since this is a Type 98, that would place the sword’s manufacture between 1938 and 1942.

So far, I haven’t found evidence that the “Shō” stamp itself corresponds to a specific manufacturing process. Is that understanding correct?

 

As for Ohmura’s page, I read the same passage. I’m fluent in Japanese (though not at an academic level), and what stood out to me was the phrase 「鋼材から生産する新作日本刀」. The word 鋼材 (kōzai) means “steel material” in a general sense. If the intent were to include all swords, even those made from tamahagane, then specifying 鋼材 seems unnecessary, even superfluous.

 

My impression is that this wording was used deliberately in contrast to tamahagane, which would align with Ōhmura’s point that gendaitō were not subject to inspection. From this, my sense is that stamped blades were not made of tamahagane, but could have been produced through fully traditional, semi-traditional, or entirely modern methods. That may explain why the NTHK and NBTHK sometimes recognize exceptionally well-made examples as nihontō, though of course, that remains controversial among collectors.

 

*

EDIT: The document Brian kind shared appears to concern swords made to very high standards for officers. It's not indicated in the translation but it dates to 1942 (Shōwa 17). The “about this file” section refers exclusively to Rikugun Jumei Tosho, though I haven’t found that designation explicitly mentioned within the document itself. So it's something to confirm.

 

The swords in question were commissioned officers’ swords (Types 94 and 98). They were required to meet high production standards, mandatorily using tamahagane, hochō-tetsu, and charcoal. If it solely refers to Rikugun Jumei Tosho, Shinoda Ujifusa (篠田氏房) does not seem to have been among them. According to Ōhmura’s website, he is instead listed as Dai-san-seki (第三席, 優秀), “Great Third Seat”, an award of excellence granted at an exhibition. However that award doesn't mean anything about how he made his other swords. It just means that he was highly skilled.

 

The source is easy to locate by searching his name: 戦時下の日本刀匠と序列.

 

EDIT n°2 : Here I have found that Ujifusa worked in Saguchi Tōken Seisakusho (佐口刀剣製作所), as the sole smith of that workshop. 

関の軍用日本刀 Syōwa-tō of Seki

 

It indicates that 関刀剣株式会社 (Seki Sword Co., Ltd.) and 株式会社濃州日本刀鍛錬所 (Nōshū Japanese Sword Forge Co., Ltd) used traditional forging techniques. But the technique of Saguchi Tōken Seisakusho isn't described. I have found one of his gunto to be papered as NTHK-NPO Kanteisho (2nd highest rank). But the Nakago isn't shown : https://new.uniquejapan.com/wp-content/uploads/2015/02/18-5-Antique-Japanese-Swords-From-Unique-Japan.pdf

 

This sword of his has also the "Sho/Sakura" stamp and was registered without issue in Japan, though it doesn't have NTHK-NPO or NBTHK papers.

【研ぎ上がり・大業物・関脇格】「氏房」68.2cm 、鑑賞に・居合・試斬刀として！！！

[SteveM]

14 hours ago, I_Kendo_It said:

their rules do not at any point mention tamahagane

 

I don't want to get too deep into the weeds, but in order to submit a sword for authentication by NBTHK, the sword must first be registered. In order for a sword to be registered, it has to be accepted as an art sword, and, in the case of Tokyo, the Tokyo metropolitan government specifies that a sword must be made of tamahagane to be accepted as an "art sword". 

 

Quote

イ 登録の条件として必要なことは、刀剣類の材料に玉鋼が使用されていること、繰り返し鍛えられ焼きを入れてあり、美術品として姿、鍛え、刃文、彫り物等に美しさが認められ、又は各派の伝統的特色が明らかに示されているものであることが必要です。

https://www.kyoiku.metro.tokyo.lg.jp/lifelong/cultural_property/registration/registration_02_01

 

Now the guys at the Tokyo metropolitan government aren't stupid, and they will certainly accept old/antique swords that are made of nambantetsu, etc... But when it comes to wartime swords they have been less forgiving. 

 

As I have come to learn, however, interpretation of the sword registration laws can vary depending on the prefecture. I do believe that most prefectures will follow the Tōkyō standards. But, as always, accommodations are made for exceptional pieces. Lately, this wiggle room seems to be expanding. If your sword can be registered, it can be submitted to shinsa. I think most prefectures will reject it, unless you can make an exceptionally strong case for your sword to be considered an art sword. 

[mecox]

@l_Kendo_It  Leonidas, interesting sword from early war Seki with Sho stamp.  Both were experienced smiths, but rather rough mei, maybe an "experiment" between colleagues?

Information and examples of both in NMB Downloads, see top of main page.

Shinoda Ujifusa in Japanese Naval Swords Part 1.

Kanetomo in Gifu Tosho List 1937 smith #29

 

[I_Kendo_It]

Interesting input, thanks, @SteveM! I wasn’t aware of the variation between prefectures.

I had read that it’s difficult to determine whether a sword is tamahagane or simply traditionally forged without scientific testing. So, while de lege and formally the rule concerns the base material, in practice it seems to mean that the sword must convincingly resemble tamahagane, and the stamp then serves as evidence against that.

 

@mecox Thanks for the information! I was also surprised by the roughness of a meishiriki-mei. Even the 友 tomo of kanetomo looks a lot like a 女 jo.

 

I doubt it’s gimei, since although Ujifusa is a recognized and experienced smith, he wasn’t among the top-level masters whose signatures were commonly faked. And the fact it carries two names makes me even more curious indeed.

 

Edit : Btw I'm impressed by your research after reading the files. Both regarding you, mecox and Bruce's work. 

[PNSSHOGUN]

The registered and papered swords are rare exceptions to the norm and I wouldn't base any final conclusions from these. For every sho/seki stamped sword with papers in Japan there were likely many that were summarily destroyed. 

 

 

[I_Kendo_It]

No worries, I'm not coming to any definitive conclusions, but rather investigating and making theories.  

[Bruce Pennington]

Leonidas,

I am, as time allows, locating the sources for my summary of the Cutlery assoc. stamping history.

 

Here is one.  On page 2 you will find Nick's translation of the Seki City website.  It is a 6 page discussion, but full of history on sword production, use of tamahagane, and stamping practice.

RJT Star stamped blades - Any Documentation?

[Bruce Pennington]

Ohmura's page discussing the use of the large Seki and Showa stamps is a bit jumbled,  Part of his discussion claims the Seki stamp was first, yet farther down the page he cites, from a memoir, that the Showa stamp was used first (which is in line with observed blades with dates).

 

http://Military Showato of Seki - Ohmura

 

"桜に「昭」刻印

　従来、名古屋陸軍造兵廠関分工場長・尾藤敬逸技術少佐の回想記「日本刀」、
　及び「関史」資料により、「関」と「桜に昭」検査刻印の切り替え時期を
　昭和17年末頃と推定していたが、昭和14年期の「桜に昭」検査刻刻印を持つ
　刀身の出現に依り、再調査を行った。
　「関伝日本刀鍛錬技術保存会」井戸誠嗣会長のご協力により、昭和15年、
　当時の関町が発行した「刀都関」誌に、『 関刃物工業組合の厳重な検査に合格
　した刀身に「桜花に昭字」の刻印が打たれ、実用刀として天下無敵の好評を博
　している 』との記述が発見された。

　これにより、昭和14年には、新たな検査刻印が使用されていた可能性が高くな
　った。
　当事者の「関刃物工業組合」の資料は未だに発見されていない。
　刻印を変えた理由、その正式な切り替え時期は未だに不明である。

　銘: 関住兼則作　「桜に昭」の刻印
　裏銘: 昭和十二二(四)年十月日

(刀身写真提供元/美術刀剣「刀心」・町井勲 様)

 

Google translate (which isn't the best):

"Engraved "Sho" on the cherry blossoms Traditionally, the memoirs of Major Keiichi Oto, director of the Nagoya Army Arsenal Sekibranch Factory, "Japan sword", And by the "Seki History" material, the switching time of the "Seki" and "Sakura nisho" inspection engraving It was estimated to be around the end of Showa 17, but it has an inscription of the "Sakura ni Sho" inspection in Showa 14 According to the appearance of the blade, a re-investigation was conducted. With the cooperation of Seiji Ido, chairman of the "Kanden Japan Swordsmithing Technology Preservation Society", in Showa 15, In the "Totoseki" magazine published by Seki Town at that time, "Passed the strict inspection of the Seki Blade Industry Association The blade was stamped with "Shoji to Sakura Flower", and it was well received as a practical sword that was invincible in the world. It was discovered. As a result, it is highly likely that a new inspection stamp was used in Showa 14 did. The materials of the "Seki Blade Industry Association" of the party have not yet been found. The reason for the change in engraving and the official timing of the switch are still unknown. Inscription: Kanenori Sekizumi "Cherry Blossom to Sho" engraving Inscription: October 12, Showa 12 (4) (Blade photo provided by / Art sword "Toshin", Isao Machii)"

[I_Kendo_It]

Thank you for sharing the material. After reviewing all six pages, I find that two prevailing theories emerge.

 

1. The theory based on the 1937 "Letter from the Chief of Police & Security Bureau of the Ministry of the Interior to the Police Chiefs of Prefectures"

This interpretation suggests that shōwatō and chō-nihontō (“super nihontō”) terms tied to stamped blades were promoted and advertised as being of excellent quality. I love the chō-nihontō term, it's such a kansai term and sounds so funny to me.  Basically, that this stamping business was initially a business ploy.

 

And so far, it appears the "Sho" stamp and "Seki" stamps were initially stamps issued by private manufacturers, before the "Seki" stamp later being tied to the army as well. That is unlike the star stamps and "Na" stamps tied to the army.

 

As the stamps originated from private manufacturers, they could be applied to any blade, regardless of the actual materials or production methods. The police mentions that some of these swords were in fact made with inferior materials, resulting in products that were brittle and prone to breakage. Thus, a stamped sword might or might not qualify as nihontō, and each blade would require individual examination to determine its status and quality.

 

That is, unless a law is found proving the contrary. That would also require establishing from primary sources that the stamps were / were not reserved to non-traditionally made swords.

 

2. The theory based on my previous interpretation, supported by Ryujin Swords’ article on tang stamps

This theory basically follows my earlier interpretation of Ohmura's writing and is supported by Ryujin Swords’ article on tang stamps. It holds that it was required by law that blades forged from tamahagane were not subject to inspection and therefore did not receive tang stamps, while blades made from non-tamahagane steels did. So according to this theory the distinction between stamped and non-stamped sword would be the use of tamahagane.

 

Ohmura’s wording hints at this distinction (by my reading), but Ryujin Swords explicitly supports the claim. If correct, it would align with their classification system:

• Tamahagane gendaitō: “true” nihontō

• Mill-steel gendaitō: forged traditionally but without tamahagane, occupying a borderline status and sometimes managing to pass shinsa by chance

• Abura-yaki-ire-tō and similar blades: mass-produced, lower-quality swords at the inferior end of the spectrum

The main difficulty with this theory is the lack of primary sources establishing such a rule. Ryujin Swords refers to a 1933 law, but unless this law can be located, the claim remains unverified.

 

I will continue searching Japanese sources to confirm whether such a law existed and will update this post accordingly.

 

EDIT: I can conclusively assert that no such law exists. It seems like a myth solely existing in the English-speaking environment. So the stamping isn't based on legal provisions, and there is no law that asserts non-tamagahane blades should be stamped. Now the question pertains to industry practices.

 

Quote

そこで関市の刀剣業者は製品のクオリティを保証するため、新しく制作された刀剣を関刃物工業組合で検査し、基準をクリアした物に証印を打つことに。近代的な製造システムによって価格を抑えられている上に、こうした品質保証制度が整えられた関市の刀剣は人気を集め、国内の市場シェアを伸ばしていったのです。

 

To guarantee product quality, Seki City's sword makers began having newly crafted swords inspected by the Seki Cutlery Industry Association. Those meeting the standards were stamped with a certification mark. Seki swords, benefiting from modern manufacturing systems that kept prices low and bolstered by this quality assurance system, gained popularity and steadily increased their share of the domestic market.

 

https://www.touken-world.jp/tips/21493

These stamps originated with craftsmen and the industry association as guarantees of quality. The army subsequently adopted them, and they were formally regulated by a Ministry of Home Affairs ordinance in 1942. While that ordinance is frequently cited as the origin of the “Sho” stamp, Bruce’s research and the memoirs cited by Ohmura prove the stamp existed earlier.

 

Next, I will research primary sources to determine whether or not the Seki Cutlery Industry Association only used these stamps to non-traditional blades.

[Kiipu]

The source of the Shō 昭 stamp identification is via Ohmura as already stated.  Bruce asked me some years back to reread the text and that is when I spotted the reference below.

関の軍用日本刀

 

With the cooperation of Ido Seiji 井戸･誠嗣, chairman of the “Seki-Den Japanese Sword Forging Technique Preservation Society” 関伝日本刀鍛錬技術保存会, a description was found in Tōto Seki 刀都関, published by the Town of Seki in 1940, that said "the blade has passed the strict inspection of the Seki Cutlery Manufacturers’ Society 関刃物工業組合 and is stamped with “Ōka ni Shōji” 桜花に昭字, and has gained an unrivaled reputation as a practical sword."

 

There is another book that I do not own yet and it is referenced below.

The Seki Tanrensho book and others related infos