Photo/IllutrationThe Tokugawa Shogunate’s official “tenkoku” seal engraving (Provided by the Tokugawa Memorial Foundation)

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The Tokugawa Shogunate’s official seal that was found 150 years after it was last used on official documents, including the 1858 Japan-U.S. Treaty of Amity and Commerce, will go on public display for the first time.

The silver “tenkoku” seal engraving will be on show at the Niigata Prefectural Museum of History in Nagaoka from Sept. 15 through Sept. 30.

The seal, which was stamped on documents alongside the signature of Tokugawa Iemochi (1846-1866), the 14th shogun of the Tokugawa Shogunate, was found in a storehouse of the residence of the Tokugawa family in Tokyo.

Known as the “Keibun Ibu,” the seal represents the shogunate’s aspiration to achieve an “ideal” form of politics with its motto, “Bun o Tateito ni Shi Bu o yokoito ni Su,” or “Let the pen be the warp and the sword be the weft.”

“The seal exudes Shogun Iemochi’s strong will to take on the responsibility of foreign diplomacy as head of state of Japan, because the shogun consciously ordered a special silver seal to be made for ratifying foreign diplomatic documents,” said Iehiro Tokugawa, an executive board member of the Tokugawa Memorial Foundation headed by director Tsunenari Tokugawa.

The square seal, 9.2 centimeters in length and width and weighing 2.7 kilograms, had been kept in a “nagamochi” oblong chest that was used to store furnishings.

The historical gem that spent more than a century and a half out of view came to light about 18 months ago when the storehouse in the residence's garden was demolished. The nagamochi was placed in the innermost storehouse, according to the foundation that now keeps the seal.

The seal was engraved by Masuda Koen, a tenkoku craftsman, at the request of the Tokugawa Shogunate in 1857.

The seal was affixed in 1859 on ratification documents of the Treaty of Amity and Commerce that Japan had concluded in succession in 1858 with the United States, Britain and France.

It also made its mark in 1867 on a document ratifying the Japan-Denmark Treaty of Friendship, Commerce and Navigation, which was concluded in 1866.

It has also been confirmed that the seal was also stamped by Tokugawa Yoshinobu (1837-1913), the 15th and last shogun of the Edo Period (1603-1867), as well as by Iemochi.