Been trying to figure out the age of my bike for awhile, Its a Nikishi kokusai. According to your system it is pre 1975 ks163424. I think I read that before 1972 they weren't called Nikishi so that puts the bike between 72 and 75. Does anyone know when they changed the Kokusai to the international, that should help narrow it down a bit more.
Here's some pic if that helps