Welcome to the Forum! I'm assuming the item is cast iron since you said you just cleaned the 'rust' off of it, although in the photos, it has a green patina. Is it iron?
Im pretty sure its cast iron was rusted rly bad the greenish might be from me cleaning it wasn't fully done with it yet when I took the pics...I do the electrolysis on my stuff.
Now that I know it's cast iron, I think it is the side corner portion of a vintage theater seat leg. Yours would have been Seat 15 on Isle B. I couldn't find a photo that matched, but the one below is similar and more fancy. Note the large hole at the bottom that would have attached to the chair frame.
After sleeping on this item, I'm thinking instead of the leg bracket on a theater seat, it could be the side bracket on the movable theater seat.
Calisdad has a good idea too with the barber's chair foot. The barber chair foot bracket and the theater seat bracket are both in the same family. A list of other items found in the same area would be helpful.
Matt, the school desk folding bracket is in the same family as the theater seat and/or barber chair movable foot panel, which is why I was wondering what some of the other items were in the area. Was there a school in the area? A barber shop?
Not rly close this house was out in the middle of know were...what I found was an old iron,some Indian heads,horse shoes,blade of thing that had the long wooden handle to cut tall grass, fire poker, grinding wheel,belt buckles, traps, insides of a clock,spoons, forks, door knob, lantern parts, old badge, steel wheel small like a hand cart kind, think piece of track to a barn door ect....