6922 Amperex PQ White label... D or O-getter? Holland or Hicksville?

They do perform beautifully.    Just a little too warm, for my tastes.     To me; the grey shield, early '60's, Siemens CCa, is joy in my BAT VK-D5.

Is the "deep low end of the 7308" an actual phenomenon or merely the perceived effect of less midrange emphasis?

@pmboyd , there is no diminished midrange in these tubes. It's the wonderful liquid mids of an Amperex tube.
The 7308 presents a more powerful, deep low-end than  the 6922/E88CC.
Don't get me wrong, all the PQ tubes have great sonics. Much more realistic and smoother and without the the grain of the Bugle Boys.

Rodman99999... Delighted to take you up on your offer. I sent you a PM.

I don't mean the 7308 may have a diminished or attenuated midrange. It's a question of balance. The suggestion has been made (ie. Joe's Tube Lore) that some iterations are more "midrange forward" than others. However, with respect to sound, I suppose perception is reality. I'm especially interested in a 6922 iteration that has a palpable midbass.