Thank you very much! Your experiences are always helpful to us.
A pair of mid-60's Mullard "large shield, halo getter" CV-2493's arrived yesterday. The mids are indeed very nice and sound exactly like a newer early-70's "dimple-getter" version I have. However, the older Mullards have slightly better bass, to my delight. They also run a little cooler than the Amperex Orange Globe 6DJ8's that I'm used to. Very nice, indeed.
In general, if possible , the oldest D getters sound the best with tube warmth but without overly distorting the sound.
Newer valves with O getters and silver shields seem to sound sonically leaner.