It seems Kowa is still around, as Robert Houllahan said. Why don't you contact Kowa directly and ask your questions about the lenses? Their website says they've been around for over 60 years.
It seems Kowa is now marketing lenses for the Micro Four Thirds camera.
Jean-Louis, you are correct, there was a 6mm Ultra T prime from CP. A Victor Duncan catalog from 1980 lists them not only as Cinema Products Ultra T Lenses in CP mount, but also in Arri bayonet mount. No 6mm lens at this time.
In a 1983 Gordon catalog they list the Ultra T primes in the CP mount for the CP-16 and GSMO cameras, and then for the Eclair ACL and NPR camera (possibly with the use of an adaptor to take the CP mount to the Eclair mount). The 6mm lens is listed. So, the lenses were made until 1983 at least.
However, in a Cinema Products catalog/price list from 10/1976, it does not list these lenses....
Gregg, I found this link in the forum from 2005.....