Mei: Koa Isshin Mantetsu saku. On the reverse side it reads Showa Kanoto-mi haru (Spring 1941).
Sugata: Shinogi-zukuri, shallow tori-zori, iori-mune.
Overall length: 34.45 inches (875.00 mm).
Nagasa: 26.18 inches (665.00 mm).
Nakago: Ubu, 8.27 inches (210.00 mm), one mekugi-ana. The yasurime are sujikai
Kissaki: Chu-kissaki, 1.20 inches (30.44 mm),.
Moto-haba: 1.20 inches (30.57 mm). Saki-haba: 0.77 inches (19.49 mm). Moto-gasane: 0.33 inches (8.26 mm). Saki-gasane: 0.24 inches (6.05 mm).
Sori: 0.71 inches (18.14 mm).
Hamon: Low suguha.
Hada: Tight ko-itame.
Blade condition: Recently polished. A few minute pinholes from past rust, but they're not serious. Sharp, with no bends, ware, chips or fatal flaws. A martial artist could safely use this for cutting straight out of the box.
Type 98 shin-gunto koshirae.
According to the Nihon To Daihyakka Jieten by Dr. Fukunaga, Mantetsu steel was developed by the Minami Manshu Tetsudo Kabushiki-gaisha (the Mantetsu Company otherwise called the South Manchuria Railway Company) at the Dairen Manchurian Railroad Factory in September 1937 specifically for sword production. Mantetsu was more than simply a railway company. By 1930 it was the largest corporation in Japan and, in the 1920s, accounted for about a quarter of the Japanese government's tax revenues. Mantetsu had built coal mines at Fushun and Yantai, harbor facilities at Andong, Yingkou and Dalian, hotels and warehouses at each station, and public utilities. Mantetsu also conducted agricultural research into development of soybean farming. In addition it had seventy-two subsidiaries such as Showa Steel Works, Dalian Ceramics, Dalian Oil & Fat, South Manchurian Glass, as well as flour mills, sugar mills, electrical power plants, shale oil plants and chemical plants. On top of that, it had a government-like role in Manchuoko, partly due to its connections to the military and the Japanese leadership. Consequently it was also concerned with state-of-the-art urban planning in Manchuoko, with modern sewer systems, public parks, and creative modern architecture far in advance of what could be found in Japan itself. Dalian, for example, was a model city.
Mantetsu thoroughly analysed the Japanese sword with a view to improving it, including reducing its susceptibility to cold fracture in extreme climactic conditions found in Manchuoko. Contrary to some sources, the steel was not made from Manchurian railway tracks, but was derived from extremely pure iron made from Manchurian iron ore by an electrical method. The steel made from this iron was highly esteemed by WW2 swordsmiths.
Having developed the steel, the Mantetsu company went on to devise an improved method of making swords. The problem with traditional methods, they found, was that the core steel was often not centrally placed and the overall construction was not consistent. To overcome this a process called moro-zutsumi was devised, whereby a rod of low carbon steel was inserted into a pipe of high carbon steel and the two forge-welded together. This method has since been rediscovered by American smiths who call it, not surprisingly, pipe welding. The welded block was then forged into a sword and hardened in water using the traditional method of yaki-ire.
For the technically minded, the skin steel (kawagane) is Carbon: 0.57%, Manganese: 0.05%, Silicon: 0.17%, Phosphorus: 0.018%, Sulphur: 0.003% The core steel (shingane) is Carbon: 0.23%, Manganese: 0.15%m Silicon: 0.21%, Phosphorus: 0.020%, Sulphur: 0.008%. The cutting edge has a hardness of Rc 72, whilst the back has hardness of Rc50. It would seem, to judge from a comparison of the hardness data, that the Koa Isshin was deliberately based on the swords of the 2nd generation Muramasa.
Mantetsu subjected their prototype sword to an appraised cutting test. The company did not tell the appraiser what the sword was. The appraiser identified it on the basis of its cutting ability as a Koto sword forged by Tadayoshi of Hizen; he considered that only a Tadayoshi sword could cut like that. Encouraged by this, Mantetsu established a sword factory and began production of swords in November 1937. Two swordsmiths, Takeshima Hisakatsu and Wakabayashi Shigetsugu, were invited to the Mantetsu facility to teach sword making to the workers. Shigetsugu returned to Japan before the end of the war and became Rikugun Jumyo Tosho.
Initially the swords were signed "Mantetsu Kitau Tsukuru Kore". The name "Koa Issin to" was coined in March 1939 by Yosuke Matsuoka, the outgoing president of Mantetsu. After that, the factory manufactured 400 Koa-Isshin swords a month. In 1944 the Imperial Army sponsored a Shinsaku-to Exhibition (newly made sword exhibition) on the grounds of the Yasukuni Jinja. One of the many sections was for "Koa Isshin" blades made by different smiths as a patriotic gesture.
Koa Isshin swords are not traditionally made swords, and are therefore not ‘art swords’. They are, however, superbly made. The construction is far more consistent than many traditionally forged Japanese blades whilst the cutting edge has a hardness of Rc 72. The hardness of the cutting edge is far in excess of all western blades and many Japanese swords; it is on a par with the hardness of an old-fashioned straight razor.
To put it another way, a Koa Isshin would, in the right hands, make mincemeat of chain mail and probably seriously damage modern plate armour. It might have some difficulty with medieval tempered plate, but that isn't guaranteed. Despite not being traditionally made, Koa Isshin swords are not inferior at all, but a superb, high quality, cutting instrument that exceeds all but the very best Koto nihonto for effectiveness. They are in short amongst the best blades that Japan has produced. Koa Isshin swords are therefore highly valued by martial artists and much sought after.
R Stein, (2011), Koa Isshin Mantetsu
R Stein (2011), Date Inscriptions - Zodiacal, 1930-1945
Ohmura (2011), The whole aspect of the Koa-Issin sword
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