I'm among those who have suggested that the "Japan" tang stamp means the knife was built by Moki. I based it on purely anecdotal evidence - the fact that the C27 Jess Horn is stamped Japan, rather than Seki City, Japan combined with the fact that Moki sold some of those under their own label, stamped Moki on the tang, rather than Spyderco, and packaged in Moki boxes. Look about 1/3rd down on
this page.
If I'm right, and assuming Moki is the only maker that does not use the Seki City stamp, then they're also responsible for all the Jess Horns, all the other versions of the Calypso and Caly, the Kiwi, and the Schempp Persians and Kris. Am sure there are others as well which I've missed, especially if they have any lock other than a midlock.
Also, FWIW, not sure all six makers are still being used. Think Masahiro did just the kitchen sharps and one or two of the smallest shops were so small that they closed when the owner(s) retired. Know for a fact Masahiro stamps Seki City, since some of the earlier Kitchen Sharps were stamped with their name as well as Spyderco's and marked Seki City, Japan. Know the G Sakai knives are stamped Seki City as well.