You have probably already discovered that 6CC1 is an erroneous marking of the first series of 6CC10, and the tubes are identical. A data sheet cannot exist, because the error was discovered before data were made public. 6CC10 has been developed as an equivalent to 6SN7GT and used interchangeably. The Russian 6H8C (cyrillic), 6N8S (latin) is another proved equivalent. Regarding sound quality, I can offer no opinion. The tubes were made for telecom and TV.
