There was supposed to be more in that reply, but Shodai Yasutsugu was a very much a Keicho era smith and Nanban Tetsu has a broad meaning not just limited to Dutch or Portugese trade.
Was under the impression that supporting information would be old Honami papers, historical records, Daimyo inventory tags, Sayagaki, and other evidence in that realm.
Certainly an impressive Sugata, as others have mentioned the deki is rather uninspiring. The more you study good swords, the more you'll start to appreciate why there are many undesirable features in this sword.
Before you get too carried away with vivid notions of generations of Samurai charging into battle on this, it very much appears to be a pack saddle:
https://www.thelongridersguild.com/oriental-wonder.htm
https://auctionet.com/en/2897564-pack-saddle-konida-gura-Japan-edo-period
Well you can be safe in the knowledge that it's a real Japanese sword, whether or not it was actually made by the smith on the Nakago is a completely different matter. As one of the most faked smiths in history, the chances of it being authentic are perishingly small.