Crown GPS-25?

I have acquired what appears to be a vintage Crown amplifier when my brother passed away. It is a mono tube amp labeled as a "Crown GPA-25". It is a table top configuration and has 2 microphone volume knobs, a phono volume knob, bass and treble knobs, and an off/on switch (knob) on the front. Is anyone on here familiar with these? I've googled it and can find nothing about it. I'd really like to know more about it.
Someone here may know, but you may have better luck at
I'm sure there are other forumsa as well