There are many different stamps seen on WWII era military issue blades. They have different meanings, uses, and histories. It would take a book to address the full story so what follows is the abridged version. The showa stamp was used to indicate a non-traditionally made blade. When you see a blade with this stamp, it means it is not a traditionally made blade. The government ordered that this stamp be used because some non-traditionally made blades were becoming difficult to tell apart from those made the traditional way. Seki stamps were placed to identify the blade as manufactured in Seki and may have also served as a local acceptance stamp. The bulk of the gunto made in WWII came from Seki. There was a veritable gunto cooperative where this business was conducted. 99% of all gunto made were not traditionally made in Seki. There may be the odd ball seki stamped blade that is traditionally made but it would be extremely rare. Some people in Japan say that the Seki stamp was the same as the Showa stamp, others say it is not certain. The Star stamp was used by the military as an acceptance stamp on blades made by the Rikugun Jumei Tosho for the military. These smiths had to pass a rigorous test to be accepted into the contract program. They received tamahagane from the military (which, as a strategic resource, was controlled by the military) and charcoal from the prefectural governor. This is documented fact. Therefore, in theory, all star stamped blades were made traditionally with tamahagane. In practice, who is to say that some smith(s) weren't hording it and passing off western steel blades??? Well, there are two good reasons why this was probably very rare: first, the blades, as mentioned, were inspected. Yoshihara Kuniie, a prominent smith of the time, worked as an inspector. You aren't going to fool him and risk being tossed out of the program. Second, people were patriotic. They were making the best blades they could for their soldiers. It may have happened, but it was most likely rare....Safe bet to say that star stamped blades are traditionally made. I have never seen a showa or Seki stamped blade pass an NBTHK shinsa. I have seen Star stamped blades pass and have owned at least one that I recall submitting and which indeed passed. Why is there so much confusion about stamps? Because nearly all Japanese collectors have shunned WWII era blades, records were destroyed, many Japanese don't much like to talk about WWII related topics, and the experts have never bothered to really research these blades because...see above. I have spent many pleasurable hours talking with several WWII era Rikugun Jumei Tosho about their experiences, spent many hours at the Diet Library digging up old records and period literature (which is difficult to get into-being a university professor made it easy), and sought out many books and papers that most people would never bother to hunt down even if they had heard of them. I also have handled hundreds, if not thousands, of WWII era blades in the past 35 years. As I result, I feel very comfortable with the above statements. As a result, my recommendation to any budding collector is to consider star stamped blades. I have never seen a bad one. They are, on average, pretty decent. Some are better than others, but you can hardly go wrong with them. Conversely, they are not on the same level as the smith's custom or private work and as such are not the best you will find, but they are honest, traditional swords that a new collector can buy with some confidence. -
Edited from an article by Chris Bowen
*It is important to remember that the word Showato means a sword made during the Showa era (1926-1989) and Gendaito refers to a sword made between 1876 and 1945. However collectors do not use the literal meanings nowdays, and for convenience, the following is the currently used meanings of the 2 terms:
Showato - A sword made from non-traditional methods, meaning not made from tamahagane. Sometimes they can still be forged and folded from other steel, and sometimes they can come close to being true Nihonto, but are not regarded as such. Most Showato refer to swords that are mass produced with little value to Nihonto collectors. The majority of wartime blades fall under this category. They are usually (buit not always) marked with an arsenal stamp such as the Sho- or Seki stamp. They are often oil quenched as this was safer and didn't lead to failure in quenching as much as traditional water quenching. They usually lack activity in the steel, and a decent hada. Note that some are made from good steel and can be remarkably difficult to identify as Showato. However these swords are illegal and may not be imported into Japan.
Gendaito - This term is nowdays used to indicate a traditionally made sword, made from tamahagane and water quenched. They are considered Nihonto and may be imported into Japan. Some smiths made both types of swords, and each must be judged on its own merits.
hope this will help it was taken from here
http://www.nihontomessageboard.com/faq.html most if not all sword questions these guys can answer browse the threads you can learn alot
