Anyone familiar with Ikeda 9 series (cantileverless kind) MC cartridges?

Impressed by the series FR-7 kinds , more in particular the FR-7 fz, I wanted to try some of the

9 C(?) kinds. I was able to buy the 9 C, mk2 but was not able to find much info about other

versions.  There are later versions so I am interested in their possible  ''added values''.