My brother in law's father in law was/is a certified gun looney. This guy shot varmints, upland birds, trap, skeet, small bore rifle....you get the picture. He has aged to the point of not being physically able to continue his shooting sports. He literally gave his son in law a huge amount of shooting/reloading gear. My bil knows very little about guns, so I told him I would help him liquidate the shooting stuff. I know what most of it is and what it is used for, but this thing has me stumped. Looks like a rest of some kind, but not much adjustment in it. The top is attached by a circular bearing that lets it rotate 360 degrees. All steel, excellent welding and finishing on it.

Sorry, the photos aren't opening for me.

Respects,
Richard

Photos work for me but I have no idea what it is.

Would a lead sled or other rest sit in it to provide a pivoting bench rest??

Rail gun mount. IMO

I am betting he put a piece of ply wood in the top and his rifle shooting bags. Walla primo swiveling rest for shooting prairie rats!!

I've heard of those things being called a 'planing table' though I know that's not what it really is.
With the rubber feet and the ability to swivel 360 degrees, I think Huntz is right on the nose with his thought. A shooting rest for helping to feed the coyotes and buzzards around pd towns.