There's a lot of variety of Kohno from the 60's. In the late 70 and on, for a long time the piano sound gets very focused.
Here's one from 68 that has the highest known number for that time period. Sakurai, et tal have seen pictures and were surprised by the construction but not surprised that finds like this comes up occasionally because kohno didn't keep records like Friedrich did.
http://www.classicguitar.com/wp-content ... ono_lg.jpg
It sounds like a Fleta!
Others have come across with kohnos that have surprisingly strong Fleta characteristics, too. It's interesting how Kohno just departed from there building towards more pianistic sound.