Authenticating Unsigned Swords: Practical Kantei Methods for Swordsmith Attribution

How to Authenticate Swordmakers Without Mei (Signatures)—Practical Authentication Methods and Technical Basis for Identifying Makers of Unsigned Blades

Among Japanese swords, there are not a few blades that do not bear a "mei" (signature)—the name of the swordmaker engraved on the blade. The absence of a mei does not necessarily mean the sword is less valuable, and many unsigned masterpieces are known to have been created by master craftsmen. So, when facing a sword that lacks the most direct clue of a signature, how do authenticators narrow down "who made it"? This article organizes the background of how unsigned swords came to exist and the practical considerations used at the authentication site, explaining the depth of the authenticating process.

Why Are Unsigned Swords Created—The Circumstances of Repolishing, Presentation, and Practical Blades

The reasons why swords lack mei are not uniform; they can be broadly divided into three circumstances.

Loss of mei through repolishing (suriage) is the most typical cause. Tachi swords made during the Heian and Kamakura periods were generally long overall, but as time progressed and the style of combat shifted to center on katana, the modification of cutting short the lower part of the blade together with the nakago (tang) became widespread. Since mei are engraved on the nakago, when the root of the nakago is removed through repolishing, the mei engraved there is lost as well. Even works by renowned swordmakers have lost their mei through repolishing and subsequently been transmitted as "unsigned" for ages.

Cases where signatures were never engraved from the start are also common. Examples are known where swords made as formal presentation or gift blades for samurai were intentionally left unsigned, where practical blades mass-produced in workshops had their signatures omitted, or where swords forged by disciples or substitutes under their master's supervision were not inscribed with signatures.

Later removal as a subsequent action—cases where mei were removed for some reason, such as cutting off the kao-mei (cartouche signature), also exist.

Against this background, the state where the nakago remains as it was at the time of manufacture is called an "ubunakago" (original tang). In authentication, the first step is to determine whether the nakago is original or repolished. If an original tang lacks a mei, it is likely that "no signature was engraved from the start," whereas if the tang is repolished, one can estimate that "a mei existed but was lost," thereby changing the course of subsequent reasoning.

Jihada and Sugata—The Naked Truth of the Blade Reflecting Place and Period

Without direct evidence such as a mei, authenticators must carefully read the indirect information encoded in the blade itself. The first of these is jihada, that is, the steel skin pattern born from fold-forging. The following are representative types of grain patterns and the schools that tend to produce them.

• Itame jihada (wood-grain pattern): Large and small eddies mixed like wood grain. Commonly found in Bizen school, with the typical example being tightly packed, beautiful itame with jinie (hardness marks) and utsuri (reflection) appearing.
• Masame jihada (straight-grain pattern): Straight grain running through it. Often appears in Yamato school blades, giving an impression of integrity and order.
• Mokume jihada (wood-knot pattern): Ring-like circular patterns mixed in. Said to be primarily seen in Yamashiro school, but there is variation depending on period and individual swordmakers.
• Ayasugi jihada (wave pattern): A distinctive grain flowing in a wave-like manner. Said to be frequently seen in Echigo school swordmakers and stands out distinctively at first glance.

However, these classifications are merely tendencies, and even works by the same swordmaker show variation depending on materials and forging methods. One cannot definitively determine locale or school from jihada alone; it is important to treat it as merely "one basis for narrowing down" possibilities.

Sugata (profile) — the depth and position of the curve, the overall length of the blade, and the cross-sectional shape of the blade (whether it is shinogi-zukuri or hira-zukuri, and the height of the shinogi ridge) — are also important clues for estimating the period. The Kamakura period features predominantly elegant profiles with deep curvature at the hips; the Nanboku-Cho period shows a tendency for increased length and higher curvature; the Edo period is characterized by relatively moderate curves and practical profiles. By combining jihada and sugata, the accuracy of period estimation increases significantly.

Hamon and Boushi—The Temper Pattern Reveals the Swordmaker's "Brushwork"

Hamon (blade pattern) is the pattern created by tempering the blade edge, and it is said to be the part where individual swordmakers' characteristics are most distinctly expressed. Broadly categorized, they divide into suguha, gunome, choji, and midare, but within these are countless finer subtypes.

What authenticators particularly emphasize is the texture of the granular activity that occurs at the edge.

• Nie-dominant: Particles are coarse, with a brightness so vivid that granulation is visible to the naked eye. Common in Soshu school blades, with chirei mixed in the jihada giving an overall powerful impression.
• Nioi-dominant: Particles are fine, spreading like mist and appearing as a soft band of light. Common in Bizen school blades, forming a gentle and refined hamon.

The textural difference between nie and nioi is difficult to convey in photographs and can only be discerned by tilting the actual blade at an angle and applying light. Therefore, accumulated experience of repeated examination of actual blades is essential for authentication.

The tempering method of the boushi (point-temper), the apex portion of the blade, is also a point of focus. The form of the boushi—how the hamon is finished at the tip: does it turn back in a large rounded manner, terminate in a small sharp manner, or extend in a long return—shows certain tendencies depending on the swordmaker or school. By combining the overall character of the hamon with the boushi, one can verify the fit to a particular school or period with even greater precision.

Tang Shape and File Marks—Traces That Remain Even When the Signature Disappears

Even in a tang where the mei has been lost, much information remains. First, the shape of the tang butt (nakago-jiri) shows tendencies depending on school and period, with multiple types identified such as "kuri-jiri," "iriyama-gata," "ken-gata," and "funasoko-gata."

Next, file marks (yasuri-me) — the finishing groove pattern applied to the tang's surface — are said to readily show the habit of each swordmaker in the angle and depth of cutting. Types such as "katte-sagari," "suji-chigai," and "kesho-yasuri" exist, and there are also tendencies in file marks preferred by particular schools.

Additionally, the number, position, and shape of peg holes (mekugi-ana) are also referenced. Blades that have undergone modification often have multiple peg holes, which in itself serves as material for estimating period and use history.

Furthermore, the color and texture of patina naturally formed on the tang over years of preservation also serves as supplementary material for age estimation. Since such information is comprehensively preserved on an original tang, it is sometimes possible to estimate a certain period and lineage based solely on comprehensive observation of the tang, even without a mei. Conversely, in the case of a repolished tang, much information on the tang side is lost, so judgment must be weighted toward elements on the blade side such as jihada, hamon, and sugata.

Narrowing Down from the Five Traditions—The Logic of Authentication and Institutional Support

In the authentication of unsigned swords, rather than directly linking individual characteristics to "this swordmaker," the basic approach is a stepwise narrowing process.

1. Understanding sugata and period context: Estimate a rough time period (Kamakura, Nanboku-Cho, Muromachi, Edo, etc.) from the overall curvature and construction of the blade.
2. Identifying the tradition: Narrow down which of the Yamashiro, Yamato, Bizen, Soshu, or Mino schools is closest based on the texture of the jihada and hamon.
3. Narrowing to a particular school or lineage: Examine which faction within the tradition is closest through the details of the hamon, the boushi, and the tang shape.
4. Estimation of individual signature (when possible): Only when multiple elements align does one reach a more definitive estimation such as "a work of the ○○ school" or "possibly attributable to ○○."

The conclusions drawn through this process can be publicly substantiated in the form of an authentication certificate from a specialized institution. Within Japan, the Public Interest Incorporated Foundation Japan Sword and Art Sword Preservation Society (NBTHK) is the representative certifying body, and it certifies authenticity, period, and maker through gradational categories such as "Preserved Sword," "Special Preserved Sword," "Important Sword," and "Special Important Sword." Even for unsigned swords, lineage or individual signatures may be certified in the form of "the ○○ school" or "attributable to ○○" based on the comprehensive characteristics of jihada, hamon, sugata, and tang; however, when proof is insufficient, only the period and country are recorded, with "unsigned" remaining.

While an authentication certificate is ultimately a record of experts' comprehensive judgment and not an immutable proof, it is considered to have higher objectivity than individual appraisals due to examination by multiple experts. When dealing with unsigned swords, confirming the presence and content of such authentication certificates is an important procedure for understanding a blade's provenance and value.

Summary—The Essence of Authentication Through Overlaying Multiple Clues

The authentication of unsigned swords begins by discerning from the starting point of "whether the tang is repolished or original," proceeds by overlaying multiple clues—the quality of jihada, the tempering of hamon and boushi, sugata, and the form and file marks of the tang—and progressively narrows from the broad framework of the Five Traditions. One cannot make a definitive judgment based on a single characteristic; the essence of the authentication process, which requires long years of experience and knowledge, lies in confirming the consistency of multiple elements while solidifying one's judgment.

The absence of a signature is not a deficiency but a trace of the history the blade has traveled. If we consider that the skill of swordmakers of old lies hidden beyond the signature lost through repolishing, the time spent in appreciation before an unsigned blade becomes rather a rich experience that engages imagination fully. In our site's column, we also encourage you to refer to the fundamental perspective of authentication that comprehensively evaluates jihada, hamon, sugata, and mei and jihada comparison across the Five Traditions.