I don't think there are many users of Altec speakers here, especially your Altec model, although back in the '70s and '80s, that's a major brand among Filipino audio enthusiasts. I've owned 3 Altec pairs in the '80s, all home speakers. They sound from warm to hot, the type that Japanese and Filipino audio enthusiasts in those days like a lot.
Your units are coaxial ceiling mounts used in auditoriums and in small theaters, not for serious home listening or studio monitoring. Based on its specs, the positive side of 619-8A is its high sensitivity, good for low-power amps, could probably be a good match for valve amps.
There's not much literature about 619-8A, in other words few fans out there, and nothing much from the Lansing Heritage website:
http://www.audioheritage.org/ where true James B. Lansing believers hang out.
It could be a rare item and if it sounds good to your ears, it should be a keeper.