This is a Korean helmet that was found in Japan. It is comprised of 34 individual iron plates that are riveted together. The shikkoro is comprised of individual small iron plates that are attached to each other with leather lacing (amazingly mostly intact). The top of the helmet has a solid post which is affixed to the helmet.
This helmet shows good age but it is possible that it is of newer manufacture and is priced accordingly. I really do not know enough about these to emphatically state the age.