They're nice little SS 5-channel mixers, can accept line, mic, or phono inputs with the right xfmrs. IIRC there are independant outs for monitors or mains. Basic 2-stack tone controls. A pair like that in a road case is cool indeed!

Tyler, The plug-in xfmrs can be used in most altec green gear as well as many other apps. The 4722s in particular see use in phono stages, as do 15095s though I consider that a waste...

Added:
Your variac treatment may have "saved" some snap-crackle-and-pop the old electrolytic caps might have made, but it would still be wise to install fresh 'lytics all around. Other than that, if it ain't broke...