Developed in the 20th century, the Koa Isshin was one of the "showato" or "non-traditional" styles of Japanese sword, where craftsmen deviated in one or more ways from the "traditional" methods. One of the deviations was in the source metal, as the demand for military swords strapped the nation's ability to produce traditional tamahagane steel. At the bottom tier, this included the use of machine-stamped stainless steel for NCO blades, but some of the best blades of the era came from an unexpected source; railroad tracks. Manufactured to withstand the massive forces brought into play by a moving freight train, rail steel needs to posses impressive hardness and ductility, both vital qualities for a sword blade. The source for the "koa isshin" blades was the rail factories in occupied Manchuria, which were soon acknowledged by swordmakers as some of the best steel for a fighting sword available. At the end of World War II the showato were classified as weapons devoid of historic or artistic value to be confiscated and destroyed, and the traditional methods enshrined in law as the only way to legally do business as a swordsmith. Measuring 36 3/4 inches in overall length, the blade measures 26 1/4 inches from the tip to the darkened copper habaki, with a smooth, nigh-perfectly straight hamon and superb color to the metal, showing an attractive frosty tone to the bevel and a mirror-quality sheen to the flats. The furniture is of the uniform Imperial Army shin gunto style, with a thick tsuba flanked by alloy seppa, a company-grade blue and brown tassel, and a green paint finished saya. The tang shows the relative newness of the blade, with some minor brown spotting on an overall mixed gray, signed with 7 symbols on the left, 5 on the right, and 4 on the spine. While not translated, the left-side signature is similar to known koa isshin examples.

Fine. The otherwise exceptionally fine blade shows some minor wear and spotting, along with a few tiny chips along the edge and evidence of light polishing; combined with the mild scuffs and stains on the wrapping and the heavier wear and flaking on the saya, this is suggestive of a weapon that saw use in the field but was well maintained. A screw is absent from the throat of the saya. A top-flight example of one of the finest combat swords of World War II.