Request for opinions on this O-suriage Tachi / Katana with Koshizori and Fumbari characteristics

[Freedomnasa]

Hello everyone,

I would like to request your expertise and opinions on this Japanese sword blade. Currently, it is mounted and functions as a Katana, but after examining the bare blade, I strongly suspect it might be an O-suriage Tachi from the Koto period.

Here are the key characteristics and measurements I observed:

• Sori (Curvature): When compared to standard curvature charts, the blade clearly exhibits a Koshizori (腰反り)profile. The deepest part of the curve starts right above the Habaki, while the upper half towards the Kissaki straightens out. It does not look like a typical Muromachi/Edo Torii-zori or Chūzori Katana.

• Nakago (Tang): The Nakago is significantly thicker and wider (Kasane/Mihaba) than the actual blade (Machi-okuri/Mihaba of the Ji). This suggests that the blade has been polished many times over centuries to remove rust/battle damage, causing the upper blade to become slimmer, while the Nakago retains its original thickness.

• Fumbari (Taper): There is a noticeable trace of Fumbari (踏ん張り) at the base, where the motohaba/motokasane is robust but tapers down towards the kissaki, which is a classic Tachi attribute.

• Mekugi-ana: It has 2 mekugi-ana, and the Nakago-jiri appears to be cut (Kiri), strongly pointing towards an O-suriage process in the past.

Given the Koshizori curve and the Nakago being thicker than the blade itself, could this be an early Koto Tachi that was cut down to Katana length? I would highly appreciate your insights on its possible school, era, or any further observations.

Thank you very much for your time and help

[Ian B3HR2UH]

If it was suriage you would expect the end of the nakago to be cut squarely ( kiri ) so this is probably unshortened ( ubu ). The quality of the mounts should tell you something about the likely quality of the blade .

[Freedomnasa]

11 minutes ago, Ian B3HR2UH said:

If it was suriage you would expect the end of the nakago to be cut squarely ( kiri ) so this is probably unshortened ( ubu ). The quality of the mounts should tell you something about the likely quality of the blade .

Thank you for your valuable observation regarding the Nakago-jiri.

Upon closer inspection of the bare Nakago in hand, I can see traces of rework at the very end. It appears that while the blade was indeed shortened (Suriage), the swordsmith/polisher carefully filed and reshaped the freshly cut tip into a rounded Kurijiri shape to make it looks clean and fit the tsuka properly, rather than leaving it as a raw, flat Kiri cut. The patina and file marks at the very tip show a slight variance compared to the upper part of the nakago.

As for the mounts, I agree with your point. The quality of the fittings can reflect the status of the blade, and I am currently looking deeper into both aspects to see how they align with the blade's history.

Thank you again for bringing up the Nakago-jiri detail, it definitely helped me look closer at the tang!

Pown.

[Scogg]

It's hard to say for certain if it's suriage, but I'm inclined to agree with Ian. That was my first impression as well.
 

I'll share a little information below; not so you have to "figure it out yourself", but rather to highlight some of the things we look for that may help confirm whether it's suriage or not. Maybe you'll be able to get some images that suggest suriage, machi-okuri, or ubu.
 

On the subject of suriage, this article has a good information about the nakago-jiri:
https://markussesko.com/2018/04/25/tensho-suriage-and-keicho-suriage/

And see this image here from a section of a Paul Martin translated article:
"The following is a translation of an article taken from Token Sugita’s website (www.token-net.com) it was written by Nobuo Nakahara sensei a kantei-shi of the Hon’ami tradition. Nakahara sensei is the author of the book due to be published in English later this year: Katana Kantei—Facts and Fundamentals."

Best of luck,
-Sam

[Lexvdjagt]

I’ve commented on this blade before but to me it looks unshortened as well, some swords were finished after shortening to appear Ubu , but this was rarely done with early koto swords. This does not immediately imply it cannot be a Tachi, a tachi as interpreted by the NBTHK is a sword (in katana size) that is in mostly or unshortened condition made before the large scale introduction of katana after the Oei period (1394-1428AD), exemptions exist and I am talking about koto Tachi exclusively. A thicker kasane on the nakago can imply age but does not equal an early koto sword immediately. The eventual reason nobody can say anything more than this about this sword is due to its condition, you cannot make a certain assessment of the age of this sword if it’s in this unpolished condition. As a side note AI won’t be able to help you significantly with this either, it will always try to give you the answer you desire most.

[Matsunoki]

48 minutes ago, Freedomnasa said:

the swordsmith/polisher carefully filed and reshaped the freshly cut tip into a rounded Kurijiri shape to make it looks clean and fit the tsuka properly,

That isn’t how it works. You don’t shape a nakago to fit a tsuka. You shape (or make) the tsuka to fit the nakago.

If a blade is shortened and or machi okuri a new tsuka would be needed to fit the completely different profile. 

[Freedomnasa]

49 minutes ago, Lexvdjagt said:

I’ve commented on this blade before but to me it looks unshortened as well, some swords were finished after shortening to appear Ubu , but this was rarely done with early koto swords. This does not immediately imply it cannot be a Tachi, a tachi as interpreted by the NBTHK is a sword (in katana size) that is in mostly or unshortened condition made before the large scale introduction of katana after the Oei period (1394-1428AD), exemptions exist and I am talking about koto Tachi exclusively. A thicker kasane on the nakago can imply age but does not equal an early koto sword immediately. The eventual reason nobody can say anything more than this about this sword is due to its condition, you cannot make a certain assessment of the age of this sword if it’s in this unpolished condition. As a side note AI won’t be able to help you significantly with this either, it will always try to give you the answer you desire most.

Thank you for your highly insightful and objective comment.

The perspective you brought up regarding the possibility of an "Ubu Tachi"  before the Oei period is fascinating and opens up a whole new angle for me. It’s a great reminder of how nuanced the NBTHK classifications can be.

You are completely right about the current condition of the blade. Without a proper polish, any attempt to definitely judge its age or school through photos is just speculation. The Hada and Hamon are still sleeping beneath the surface. My main goal right now is simply to gather as much educational insight as possible from experienced collectors like you before making any further decisions, such as sending it for a professional polish (Togi).

Also, haha, your side note about AI is spot on! I’ve noticed it loves to validate whatever theory I throw at it, which is why I value the grounded, real-world expertise from this forum much more.

Thank you again for sharing your deep knowledge. 

 

Pown.

[Freedomnasa]

54 minutes ago, Matsunoki said:

That isn’t how it works. You don’t shape a nakago to fit a tsuka. You shape (or make) the tsuka to fit the nakago.

If a blade is shortened and or machi okuri a new tsuka would be needed to fit the completely different profile. 

Ah, you are completely right. Thank you so much for correcting me on that!
I see now that I had it backward. It makes perfect sense that the tsuka is always custom-made to fit the nakago, and a new one would be required after any alteration to the blade.
Thank you again for sharing your expertise.

 

Pown.

 

[Freedomnasa]

1 hour ago, Scogg said:

It's hard to say for certain if it's suriage, but I'm inclined to agree with Ian. That was my first impression as well.
 

I'll share a little information below; not so you have to "figure it out yourself", but rather to highlight some of the things we look for that may help confirm whether it's suriage or not. Maybe you'll be able to get some images that suggest suriage, machi-okuri, or ubu.
 

On the subject of suriage, this article has a good information about the nakago-jiri:
https://markussesko.com/2018/04/25/tensho-suriage-and-keicho-suriage/

And see this image here from a section of a Paul Martin translated article:
"The following is a translation of an article taken from Token Sugita’s website (www.token-net.com) it was written by Nobuo Nakahara sensei a kantei-shi of the Hon’ami tradition. Nakahara sensei is the author of the book due to be published in English later this year: Katana Kantei—Facts and Fundamentals."

Best of luck,
-Sam

Thank you so much for this reply and for sharing the article! I don't mind figuring it out at all—this is exactly the kind of educational insight I was hoping to find here.

The information regarding Tensho-suriage vs Keicho-suriage in Markus Sesko's article is incredibly eye-opening. It perfectly explains how a shortened blade could still have a beautifully reshaped, rounded Nakago-jiri instead of a raw Kiricut, which was exactly what confused me at first.

Now that I know what details to look for (like the specific direction of the file marks and the patina transition near the tip), I will try to take closer, high-resolution photos of the Nakago under better lighting and share them here again.

Thank you for being so helpful and guiding me on what to look for!

[Matsunoki]

Looking again…..to me it does not look suriage but it does look machi okuri and the reason for that could be in the image below? 

[Jussi Ekholm]

Do you have the blade length and tang length with habaki taken off from the sword?

[Freedomnasa]

6 hours ago, Matsunoki said:

Looking again…..to me it does not look suriage but it does look machi okuri and the reason for that could be in the image below? 

Wow, thank you for pointing that out! 

[Freedomnasa]

10 hours ago, Jussi Ekholm said:

Do you have the blade length and tang length with habaki taken off from the sword?

The blade is 68 cm long, the tang is 17.5 cm long, and the handle is 23 cm long. I'm wondering if it might be a Katate-uchi?

[Freedomnasa]

Regarding this sword, I have some interesting information. The picture shows an example of a Mihara-style hilt, similar to the one I own. Is it possible that the sword I have might be from the Mihara craftsmanship?

[NotANinja]

17 hours ago, Freedomnasa said:

Regarding this sword, I have some interesting information. The picture shows an example of a Mihara-style hilt, similar to the one I own. Is it possible that the sword I have might be from the Mihara craftsmanship?

Not really, mekugi-ana placement maybe but nakago-jiri is different.

[Freedomnasa]

"Hello everyone. Today I'm sharing the detailed dimensions of this blade. Take a look at the proportions:

~The base is 28 mm wide, tapering to only 17 mm at the tip (a difference of 11 mm).

~The thickness slopes from 7.0 mm down to 3.5 mm (a reduction of half).

~The tip is tiny (Kogissaki).  I measured it, and the dimensions lean heavily towards an ancient #Tachi. It doesn't seem like the specifications of a later Katana from the perspective of those of you who collect Koto swords. Do you think these proportions... are they the true DNA of a Tachi? Or are there any Katanas from other eras that have such a sharply tapered and sloping blade?"

[Geraint]

Dear Pown.

 

In your first post you show an image of the mune of your blade at the habaki which shows a considerable thinning of the blade just above the nakago.  This suggest that as well as being machi okuri your blade has received several polishes.  This may indicate that the blade is older or that it has received some damage and needed to be repolished quite harshly.  In either case the shape of the blade now is not what it was when it was first forged.  As the sword is out of polish we are not able to examine the boshi but I suspect that it would be very thin, a consequence of the kissaki being polished down.  Polishing also changes the sori to some extent so drawing conclusions from this blade is problematic.

 

Fumbari is a specific condition relating to the blade narrowing just above the habaki, this would be severely effected by either suriage or machi okuri.  Using this sword to explore the features of tachi and katana is an interesting exercise but arriving at a definitive conclusion is not going to be an option.  In it's present state most people would regard it as a mumei katana.  Might it have been a tachi?  Well, Colin pointed out a good reason for the machi okuri, the nakago does not suggest that it is suriage and it is mumei.  It has seen quite a bit of wear and tear and we don't have indicators from the hamon and jigane so for me the most supportable conclusion is that it is a tired old katana.

 

I hope that some of that helps.

 

All the best.

[NotANinja]

18 hours ago, Freedomnasa said:

"Hello everyone. Today I'm sharing the detailed dimensions of this blade. Take a look at the proportions:

~The base is 28 mm wide, tapering to only 17 mm at the tip (a difference of 11 mm).

~The thickness slopes from 7.0 mm down to 3.5 mm (a reduction of half).

~The tip is tiny (Kogissaki).  I measured it, and the dimensions lean heavily towards an ancient #Tachi. It doesn't seem like the specifications of a later Katana from the perspective of those of you who collect Koto swords. Do you think these proportions... are they the true DNA of a Tachi? Or are there any Katanas from other eras that have such a sharply tapered and sloping blade?"

Yes, I can provide evidence for I myself have a blade with prominent fumbari, a ko-kissaki and significant taper which (in the absence of any paperwork) this board (and higher up members of the to-ken society GB) decided on it being mid-late muromachi circa 1500 ish. Mine has I would say a slightly better chance of being older than that because the nakago is cut straight off at the end. I will agree with you that it is romantic to think in these instances where blade geometry is similar to ancient blades to believe you may have hit the jackpot but the likelihood is that you haven't - be careful to not try and search hard to find evidence that supports your theory while ignoring the counter evidence. Don't worry I am guilty of the same with my blade! Looking at the facts: it has a decent amount of sori, it tapers significantly already, it has fumbari, the nakago-jiri is finished and not cut straight across, and it is already koshi-zori. These things don't point to an o-suriage blade, and the evidence for it being is speculative it could be either way with what others have said. My guess is mid-late muromachi but without jigane and hamon no idea on school. Here's the link to the post I made:

 

https://www.militaria.co.za/nmb/topic/53020-latest-aquisition-in-relatively-poor-shape-given-to-me-by-family-as-they-know-i-love-these-things/#comment-554789

Edited Wednesday at 07:04 PM by NotANinja
Added link to similar blade post

[Freedomnasa]

On 7/23/2026 at 1:30 AM, NotANinja said:

Yes, I can provide evidence for I myself have a blade with prominent fumbari, a ko-kissaki and significant taper which (in the absence of any paperwork) this board (and higher up members of the to-ken society GB) decided on it being mid-late muromachi circa 1500 ish. Mine has I would say a slightly better chance of being older than that because the nakago is cut straight off at the end. I will agree with you that it is romantic to think in these instances where blade geometry is similar to ancient blades to believe you may have hit the jackpot but the likelihood is that you haven't - be careful to not try and search hard to find evidence that supports your theory while ignoring the counter evidence. Don't worry I am guilty of the same with my blade! Looking at the facts: it has a decent amount of sori, it tapers significantly already, it has fumbari, the nakago-jiri is finished and not cut straight across, and it is already koshi-zori. These things don't point to an o-suriage blade, and the evidence for it being is speculative it could be either way with what others have said. My guess is mid-late muromachi but without jigane and hamon no idea on school. Here's the link to the post I made:

 

https://www.militaria.co.za/nmb/topic/53020-latest-aquisition-in-relatively-poor-shape-given-to-me-by-family-as-they-know-i-love-these-things/#comment-554789

Thank you so much for sharing your personal experience and that valuable reality check!
You made a very fair and grounded point about Confirmation Bias—it’s definitely easy to fall in love with the idea of a blade being older or rarer than it might actually be. Your observations on the nakago-jiri not being cut straight across, along with the koshi-zori and overall geometry pointing toward Mid-Late Muromachi (Koto era around 1500), make a lot of practical sense.
I really appreciate the link to your thread as well; it’s super helpful to study a similar piece with a comparable profile. As you rightly pointed out, without clear sight of the jigane and hamon, any attribution to a specific school remains purely speculative for now.
Thanks again for your honesty and for helping me keep a balanced perspective as I learn!
Best regards,
Pown"