Siemens CCa: Gray and Silver riser differences

Heavily affected by age. It's not the colour. The silver risers are the older, and much better sounding, tubes. Maybe the air was better in the plant. I have both and stick with the silver risers in my AA 3A.

Slightly off-topic, but not really too far....Does anyone have a link to a diagram of a tube with various parts named; IOW a guide to tube anatomy.

I also have never read a reasonable explanation as to why the early grey riser versions bettered the later silver risers. Doing a search on the Tubes Asylum, I read that some have said that the early versions had a .028 diameter frame grid. Who knows if this was the main difference. I have recently put the question up on the tube asylum asking why and how regarding the differences, so maybe someone will give a good explanation. We'll see.

Tvad,

Can you recommend a reliable source for grey riser CCas?
Do those that tend to the microphonic react this way in all amps? Aside from microphonics could one expect consistent quality from all grey shields or are there best of the best versions in your view (again, perhaps by virture of date)?