[QUESTION] Looking for info on Mesa brand 12AX7-A tubes.

Does anyone know anything about them? I [tried to take pictures](https://imgur.com/a/CINgqiB) but they don't turn out well. The markings say STR 12AX7-A, just in case the other parts are hard to see, I just wanted to get the MESA part in there as it's not normal to be in that font and be written vertically when I was searching Google images for Mesa 12AX7's.