These account books, including “Yorozu Oboecho” (general memoranda), were found at a gunsmith’s residence in Sakai, Osaka Prefecture. (Provided by the Sakai city government)

SAKAI, Osaka Prefecture--A trove of documents has revealed a detailed picture of the thriving gunmaking industry during the Edo Period (1603-1867), although it is known as a time of peace and prosperity.

The finding comes from a report published by city authorities and Kansai University, which jointly studied more than 20,000 documents found at a gunsmith’s residence here in 2014.

Many feudal lords continued to purchase firearms even in the mid-Edo Period, and gun transactions grew under the political instability of the late Edo Period, the study showed.

"The set of documents, which is like a time capsule covering three centuries, is highly valuable," said Yutaka Yabuta, a professor emeritus of early-modern Japanese history at Kansai University and a member of the research team. "They contain enough to rewrite the history of guns in Japan."

Sakai evolved into Japan’s leading gunmaking hub during the Warring States period (late 15th to late 16th centuries).

The building served as a residence, workshop and store for a family of gunsmiths, whose members inherited the professional name of Inoue Sekiemon generation after generation.

The highlight of the finds was a set of documents titled “Yorozu Oboecho” (general memoranda), which recorded the orders received, deliveries and price settlements of firearms.

Sixty-one bundles of similar documents were found to survive from a period between 1802 and 1868.

The account books indicate, for example, that the workshop sold 469 guns in 1866, the year before the demise of the Edo shogunate, for a total turnover of 3,029 ryo, which would be approximately 300 million yen ($2.74 million) today.

Surviving documents also show that orders were being received from feudal lords and other members of the warrior class.

The number of orders taken, including those for repairs, grew toward the latter half of the Edo Period and peaked at more than 280 in 1839, two years after Oshio Heihachiro rose in arms against the authorities in Osaka.

Another document showed that Sakai’s gunsmiths had transactions with 239 feudal lords and “hatamoto” warriors (direct retainers of the shogun) based in areas ranging from the Tohoku region in the northeast to Kyushu in the southwest as of 1842. The Inoue family accounted for 61 of those transactions, controlling a top share.

It is believed the Inoue family began producing firearms in the early Edo Period, when five other families constituted a group of leading gunsmiths in Sakai. There was apparently a power shift in the mid- and latter Edo Period, with the latter families falling into a decline.

It has also been learned that Sakai’s gunsmiths proposed that they offer a gun capable of shooting a 1-kan (3.75-kilogram) cannonball to the authorities free of charge for the defense of Japan’s coasts in 1853. It was immediately after U.S. Commodore Matthew Perry visited Japan.

The gunsmiths successfully test-fired a gun along the coast of Sakai two years later.

Finds from the residence also included 40 guns, which are being studied by the Sakai City Museum.

The Inoue family residence, which was rebuilt after being destroyed by fire during the Summer Siege of Osaka Castle in 1615, is one of the oldest surviving traditional townhouses in Sakai.

The Inoue family has donated the building to the city government, which is planning to allow public access to the property in 2023.