I'm in continental Europe. And?
Interesting you measured their later drivers.
I heard the doped cambrics actually improve with age.
It's something I can perfectly understand.
I have a number of the CG type drivers - mostly 8" but use a pair of their 15" and 12" without the "T" option on a daily basis..
The CG8Ts, I orginally bought direct from the factory.
People have never failed to be astonished by the sound ever since I installed them in my own cabinets years ago.
It's really astonishing to think they are 50yrs old and work so well.
In fact, they could not understand the sheer midrange clarity the dual cone speakers made with comparatively low power amps years and years ago (5W per ch).
It appears Allan speaker drivers were a total sleeper for a long time.
A whole load of Yorkshire based companies*existed that were dedicated to making typically British sounding hi quality stuff, - not loaded with the PR, and hype that exists today.
They do require very careful attention to roll off and cabinet design, (eg. get rid of boxiness), but many people have compared them with other full range drivers such as Coral, Fostex, Seas, AD, TB, Visa, Lowther etc and found they sound far better than all of them. with nothing like the characteristic harshness, and foggy low range you get with those.
These old drivers are like the later ones, except with really soft surrounds, so I suppose ideal for a 60s nostalgia set up.
Who knows?
I removed them because I needed CG8T in those vertical bass reflex by connoisseur*.
That improved them a lot.