This is only my understanding.
The word Gendaito means modern sword. And at the same time they are defined as the nihonto made after 1876 (or 1868 by other opinion) in this field. Any way the category is based on the period in that the sword made.
On the contrary, the word Shinsakuto has general meaning of newly made sword. So, every sword was Shinsakuto when it was made, even though it is Koto. But of course they did not use the same terminology at their era, I think.
Then, how many years a new sword can be called Shinsakuto? I really do not know, 1 year, 2 year, or more...?
But I thnk that say 20 years old sword is not called Shinsakuto, even if the smith is still alive. And I also think that even if the sword is young enough say 1 year old, it is not called Shinsakuto when it is secondhand.
