As I have noted a few misconceptions of Japanese sword making eras and their terminology, I thought a brief outline for the collector and student might be informative.
KOTO (Old Swords)
The Japanese sword as we know it today was first introduced in the late 9th century. In this early era, sword making developed in to five basic schools of forging and construction technique, These sword making traditions spread along the five main trade routes in Japan.
THE YAMATO SCHOOL
This is the oldest school of sword making and began in the area around present day Nara
THE YAMASHIRO SCHOOL
The second oldest tradition found in Kyoto, the old home of the Imperial Court
THE BIZEN SCHOOL
The third oldest group located in the area surrounding the Village of Osafune near the modern day City of Okayama.
THE SOSHU SCHOOL
The fourth ooldest group located in the area around Odawara. The founding of this tradition is ascribed to the famous swordsmith, Masamune
THE MINO SCHOOL
The youngest of the five traditions, this group came from the Soshu tradition and worked in the area around the City of Seki.
Collectors of WW2 Japanese swords wil recognize this name as a majority of the military blades were made in this area.
The location of all of these groups were based upon the necessities for their work. This included ample water, sand iron ore and a customer for their work. As time when on, offshoot subschools of these five groups sprang up in various locations along the trade routes. the finest Japanese swords were made during this era.
The end of the era of old swords is generally considered to be the Oei Period(1394). Swords produced after this era are referred to as SUE KOTO or late old swords. With the onset of the Oei period, Japan suffered through a series of civil wars. During this period, the quality of sword making fell off due to the great demand for weapons. Many mass produced blades from the era survive due to the great numbers produced. Private order blades were of finer quality. However, blades from this era seldom rivaled the quality of earlier work. The end of civil war brought an era of peace to Japan. The unification came under the rule of the Tokugawa Shoguns, who moved the center of politics from Kyoto to their home city of Edo, which is today modern day Tokyo. The end of the era of Koto is generally established to coincide with the rise of the Tokugawa in the Keicho era, which began in 1596.
SHINTO (New Swords)
The establishment of the Tokugawa Government brought great changes to Japanese sword forging. The demand for swords fell in the rural provinces, causing a migration of swordsmiths to major centers of government and trade such as Edo, Osaka, Kyoto and Hiroshima. With this migration came a meldign of the five traditions in to sword making. Foreign steel began to be used in lieu of the traditional tamahagane derived from sand iron ore. Much of the steel was imported from India through trade with the Dutch. As the era of peace settled in, the need for new swords diminished. By the mid 17th century, we begin to see the inception of body cutting tests appearing inlaid in gold on the tangs of fine blades. As there was no war, there was no manner in which to test the keeness or strength of a blade. Official testors would use these blades for executions or the severing of the bodies of the dead. As the demand declined, so did the quality of the Japanese sword. By the begining of the 18th century, the quality of what swords being produced had fallen to an all time low.
SHIN SHINTO (New New Swords)
With the begining of the Kansei era(1789), a swordsmith named Suishinshi Masahide appeared as a Renaisannce sword smiths. He traveled around Japan obtaining many students to whom he imparted a new growth in the quality of sword making. This era of growth continued until the end of the Tokugawa era and the establishment of a constitutional monarchy with the Meiji period in 1871. In 1876, the wearing and manufacture of swords was outlawed. Swordsmiths and those involved in related trades were forced to find new trades for survival. With the rise of a modern Japanese military, the art of sword making was revived in 1896. However, the lack of study and work for twenty years produced few swords of any merit.
GENDAITO (New Swords)
The current era of swordmaking began as previously stated in 1896. During the 1930's, production of swords markedly increased due to demand and sponsorship from the Imperial Japanese Army. The IJA went as far as to open a traditional forge high in the mountains of Central Japan to produce tamahagane. This traditional material was sent to the IJA sponsored sword forge at the Yasukuni Shrine in Tokyo. Following the end of WW@, swordmaking again ceased until the early 1950's, when a few swordsmiths began working agin under the sponsorship of wealthy patrons. The work continues until today.
Please note that the transitions as listed in this document were gradual and the era dates are given only as a reference point. I hope this information is of some merit to the collector and begining student.