Siemens-Rohne Cca not nearly as good as Siemen-HalskeWarrenh, be careful. My first experience buying the siemens CCa was not good. I bought a NOS NIB pair from a member here on agon. He told me they were made in the 1960s. After listening to the pair of tubes, finally in the correct row of importance of my Sonic Frontiers Line One preamp, I discovered the highs sounded a little rolled off bass a little light weight. Turned out this pair of CCa were from the 70s. What to look for, the 70s tube uses a small round support rod to support the hallow getter.
Siemens_Halske between 59 to 72 are the real deal and are the way you guys have described.
The white label Amperex PQ 6922 USA made tube of the middle to early 60s will blow the 70s Siemens CCa tube away hands down.
The early 1960s Siemens CCa (all grey plate) is another story. As other have said a great sounding tube. The later 60s Siemens tube sounds as Virgo_ref described, still not too bad a sounding tube I never noticed the brightness, but it just lacks the fullness of the midrange of the earlier CCA tube.
The real deal
http://gon8.audiogon.com/i/c/f/1115367414.jpg
For the money, JMHO, you can't beat the white label middle to early 60s USA made used Amperex PQ 6922 tube. I just recently picked up a used pair made in 1965 for $42.50 on ebay. They test like new, and are dead quiet.
That brings up another subject. Buy a decent tube tester.
jim