It's actually the base that used to hold our "huge" 36" CRT TV. That TV weighed well over 200 pounds, and this handled it with ease.
There's a metal platform that the TV sat on. That platform can pivot 360 degrees around on a nice bearing. Then that entire platform is on heavy duty drawer slides that let the whole thing slide back and forth about a foot. That in turn is attached to a metal frame that was bolted to a shelf.
If anyone has a use for this thing, let me know and it is yours. Also if you want more details or pictures, just email me and I will answer.