Is there a significance to the use of a kokuin vs. a kakihan?
Some resources state that a signed blade with kokuin seal may be made by the swordsmith's apprentice, student or simply have been produced by his foundry.
For example, the nihonto site states "(Asano) Kanesane swords which bear a Showa or Seki tang stamp are not considered traditionally made (gendaito)" and the presence of the kokuin does not mean the swordsmith made the sword himelf.
I have also seen blades with both kakihan and kokuin as well as blades signed by the same swordsmith, forged in the same month and year (and with his age), one with a kokuin and the other with a kakihan.
So, I'm confused. Is there a rule of thumb?