I soaked and prepped these corners for polishing. They were coated with varnish like the knobs and backers were. It came off after soaking overnight in EvapoRust in an ultrasonic cleaner. When I started to polish them, I noticed the extreme wear on the bottom surfaces of the bottom corners. It looks like it was dropped and dragged repeatedly across a concrete floor or other abrasive surface.
I'll be adding feet to the bottom in place of the bottom screws anyway, so it will not be noticeable on the final restoration.