Spotting Fakes — An Introduction to Authenticating Japanese Swords

The Existence of Counterfeits—The Greatest Risk Collectors Face

Unfortunately, counterfeits exist in the world of Japanese swords as well. While the sword market has a history spanning more than a century of development, an equally long history of forgeries has accumulated alongside it. Counterfeit works include gimei swords with forged signatures of master smiths, atomei swords where signatures were added to originally unsigned blades, and awasemei where blade bodies from different periods were combined with nakago from different eras—the methods of forgery are diverse.

In particular, works by renowned smiths and masterpieces designated as Important Swords have strong incentives for creating sophisticated forgeries, as they command high valuations. In a market where transactions of millions to tens of millions of yen are not uncommon, distinguishing authentic from counterfeit literally determines a collector's financial well-being. Possessing fundamental knowledge of authentication is an indispensable defensive measure for modern collectors.

Gimei (False Signatures)—The Most Widely Circulated Forgeries

Gimei are created by carving the signatures of famous smiths onto blades after the fact. This is the most common form of forgery in the sword market and has a history of continuous practice since the Edo period. Because swords bearing the signatures of renowned smiths command significantly higher market values, there is a constant temptation to add signatures and inflate value regardless of the blade's quality.

To distinguish sophisticated gimei, it is necessary to observe not only the calligraphy and character shape of the signature but also the type and fine detail of the yasuri marks on the nakago, as well as the position, depth, and balance of the signature in combination. Furthermore, it is essential to verify that the period of activity of the smith recorded in the signature matches the technical method and shape of the blade. If a signature of a Kamakura-period smith is carved into an Edo-period blade, the mismatch in technique and period becomes an obvious contradiction.

Atomei (Later Signatures)—Signatures Added to Unsigned Blades

Atomei are created when someone from a later period carves a signature into a blade that was originally unsigned. The fundamental motivation for this alteration is the reality that signed swords command higher market values than unsigned blades.

The most typical way to identify atomei is the unnaturalness of the color and condition of the nakago. Normally, the nakago develops a deep rust color called "kosabi" (ancient rust) through centuries of exposure to air. When atomei is present, the newly carved signature portion often displays a color distinctly different from the surrounding kosabi. However, sophisticated forgers hide this discrepancy by artificially coloring the entire nakago or imitating rust through acid treatment. Detecting such alterations requires observation under multi-directional lighting and professional expertise.

Ooyasuri Mushin and Awasemei

Ooyasuri mushin refers to blades where the original signature has been lost due to extensive resharpening of the nakago. While this is not technically a forgery, the absence of a signature makes it difficult to identify the smith. This is commonly seen when tachi were shortened for use as uchikatana.

Awasemei involves combining a blade body and nakago that are originally separate as if they were from the same sword. This is more difficult to distinguish than gimei and requires comprehensive evaluation of whether multiple elements—the period character, steel quality, and degree of wear of the nakago and blade—are consistent.

Four Perspectives for Distinguishing Authentic from Counterfeit

Four basic perspectives for authentication are as follows. First, verify that the jigane and hamon are technically consistent with the period and school of the smith recorded in the signature. Second, verify that the rust color on the nakago is "kosabi," showing natural patina developed over centuries. Third, examine in detail whether the type and expression of the yasuri marks carved on the nakago match that smith's distinctive style. Fourth, confirm that the overall shape, kasane (thickness), sori (curvature), and mihaba (blade width) possess the natural beauty appropriate to the period. Only by comprehensively verifying these four perspectives can one approach a judgment of authenticity.

NBTHK Certificates—Assured Peace of Mind

Self-directed authentication is extremely risky, even for experienced collectors. Professional appraisers specializing in Japanese swords sometimes find it difficult to distinguish sophisticated counterfeits completely. Therefore, purchasing only swords with NBTHK (Japanese Sword and Art Preservation Society) certificates is the most reliable defense available to collectors. NBTHK authentication is issued after review by multiple experts in a consensus-based process and is globally recognized as the highest authority in Japanese sword authentication today.

NBTHK certificates have four levels: Preserved Sword, Special Preserved Sword, Important Sword, and Special Important Sword. Higher-tier certificates undergo more rigorous review and carry greater market value. Before purchase, it is important to verify that the contents of the certificate (including the smith's name, period, and shape specifications) match the actual blade. Ultimately, purchasing from a trustworthy sword specialty dealer becomes the greatest defense strategy.