The motivation for kicking off this thread, was not to be argumentative, but to once and for all settle, at least in my mind, the definition of nihonto, which seems means different things to different people.
As you may deduce, I love my Showa/Gendai period swords.
It started a few weeks ago when my teacher (of swords) was trying to educate me on the features of Bizen, Soshu, etc on some very old blades, all with Tokobetsu Hozon papers.
After studying the hada, habuchi, and hataraki on the nihonto he had pulled out of his collection, I said "hang on a minute", I have swords made in the 1940's that have these features.
Hence my question, if it is impossible to determine what material a blade was made from, and they exhibit the 4H's, and they were made in Japan, then are they not nihonto?
Some may argue that WW2 swords made from tamahagane have star stamps. But Yasukuni Minatogawa, Sadakatsu to name a few do not.
I have heard about true accepted nihonto, that in one case was made from 200 year old nails, and another from smashed up old iron tea pots.