Types of Gimei and Authentication: The Sword Industry's Approach to Detecting False Signatures

What Are Gimei? ——The History of "Lies" Hidden in Arie Blades

In evaluating the value of Japanese swords, the mei (signature) of the swordsmith carved into the nakago (tang) is one of the most crucial factors for assessment. Swords bearing the signatures of master craftsmen can command prices from millions to tens of millions of yen on the market, and this substantial economic value has historically created fertile ground for the production of forged signatures. Gimei refers not to authentic signatures carved by the swordsmith themselves, but to signatures that were later inscribed or altered by others.

The history of gimei runs parallel to the history of Japanese swords themselves. Already during the Edo period, a "famous blade boom" had emerged, with swords bearing the names of renowned smiths such as Masamune, Nagamitsu, and Yoshihiro in circulation. The custom that a blade could not be recognized as a masterpiece without a certificate of authenticity called "origami" issued by the Honami family arose as a countermeasure against the widespread circulation of gimei. Even in modern times, arie blades that do not pass examination by the NBTHK or the Nippon Katana Preservation Society contain gimei at a certain rate, and experts at the forefront of authentication are devoting considerable energy to their exclusion.

Primary Classifications of Gimei ——Five Patterns

Gimei can be broadly classified into five categories based on production methods and motives.

①Atoumei (Later-Applied Signature): Signatures applied later to mumeizai (unsigned blades). The blade itself is often an authentic ancient blade or masterpiece, and the typical example is adding a forged signature to an unsigned work by a master craftsman to inflate its value. The period characteristics of the nakago and the newness of the signature tend to differ, making this category relatively easy for experts to detect.

②Kaizanmei (Altered Signature): An existing signature of a relatively obscure swordsmith recarved into the name of a famous smith. For example, altering "Nobufusa" to "Nobuhide"—most alterations involve signatures with similar character forms. When performed with old rust attached, discrimination becomes difficult.

③Togidashimei (Polished-Out Signature): A technique of polishing a nakago whose signature has become difficult to read due to rust or dirt, and presenting non-existent brushwork as a "discovery." When the polishing traces are too uniform, suspicion is heightened.

④Daitsukemei (Transferred Signature): Reusing a nakago originally attached to a different blade and replacing the blade itself. The period and era characteristics of the nakago and blade often do not match, making the position of the mekugi hole and the degree of nakago corrosion important factors for determination.

⑤Keizusashomeimei (Lineage Fraud Signature): Impersonating a master craftsman of an actual lineage with few surviving works, and adding a signature to an unsigned blade with similar workmanship. Most cases target regional smiths with limited historical records.

How Experts Distinguish Gimei

The authentication of gimei is conducted along two axes: evaluation of the blade's workmanship and analysis of the signature's calligraphic style and carving method.

Verification of consistency with the blade is the fundamental first step. For example, if a blade with characteristic Bizen-den jihada (itame skin and choji-midare hamon) bears the signature of Masamune, a master craftsman of the Soshu-den, suspicion immediately arises. Masamune's blades are characterized by nie-deki jihada and distinctive gunome-midare, which are physically incompatible with Bizen skin.

In calligraphic style analysis of the signature, comparison is made with a database of each smith's distinctive character forms, tagane application, carving depth, and character spacing. Oshigata documents since the Honami family and examination data accumulated by the NBTHK are consulted. Characteristics of brushwork are relatively abundant for smiths from the mid-Edo period onward, but reference materials are scarce for ancient swordsmiths, making determination difficult.

Observation of tagane marks is also an important clue. The tagane used by pre-Edo smiths were often broad chisels, tending to create U-shaped cross-sections in the carving. Those forged in modern times often have V-shaped cross-sections, which can sometimes be distinguished under magnification.

The rust formation pattern cannot be overlooked. On authentic old signatures, rust of similar age adheres to both the interior of the signature grooves and the nakago surface, but on later gimei, the rust inside the grooves is uniformly thin or retains an artificially colored, unnatural appearance.

Economic and Legal Issues of Gimei in the Industry

Gimei inflicts serious economic loss on the sword industry. Arie blades can command prices several to tens of times higher than mumeizai, and in transactions involving gimei, buyers suffer substantial damage. Particularly in modern times, with the increase in overseas buyers, fraudulent transactions targeting purchasers unfamiliar with Japanese authentication culture have become problematic.

Legally, selling gimei as "authentic arie blades" can potentially be prosecuted as fraud (Criminal Code Article 246). In fact, there have been cases in the past where dealers selling gimei blades at high prices have been prosecuted. However, there are many cases where it is difficult to determine whether something is gimei or not, such as later signatures that were in good faith restoration in ancient times, and legal judgment is influenced by individual circumstances.

The Japan Sword Merchants Association and industry organizations recommend the presentation of certificates of authenticity in member transactions and informally encourage treating NBTHK-unapproved arie blades as equivalent to mumeizai. This is an industry effort for voluntary transparency assurance, but it lacks legal force and has limitations in enforcement.

Reducing Gimei Risk ——Practical Measures for Buyers

When purchasing arie blades, the following step-by-step verification helps reduce risk.

First, verify the presence or absence of a certificate from the NBTHK or the Nippon Katana Preservation Society. Both organizations conduct comprehensive examinations including the authenticity of arie blade signatures, and blades awarded ratings such as "Exceptionally Important Sword" or "Important Sword" are virtually certainly not gimei. However, since forgery of certificates themselves exists, verification by inquiring the issuance number with the organization is advisable.

Next, consulting multiple experts is also effective. It is not uncommon for another specialist to have a different opinion even if one expert judges a signature to be authentic. Obtaining second opinions from multiple experts is becoming established as industry practice in high-value transactions.

Finally, the perspective of evaluating value as an unsigned blade is also practical. Even if the authenticity of the signature is questionable, if the blade's workmanship is excellent, it is recognized as having a certain value as a mumeizai. Purchasing with full awareness of gimei risk and transacting at prices based on "blade evaluation disregarding the signature" is also one option taken by experienced collectors.