Basically they are steel discs from a discus plow... a farm implement that turns the soil.  Farmers replace the rows of discs from time to time and they generally just sit in a field or barn and rust.  I'm finding them in Oklahoma which holds significance for me having been raised there and having spent 3 or 4 summers driving a tractor pulling this implement.  Each piece is comprised of 2 disks welded together to become a "flying saucer" shape which then goes on a steel bracket to hold it vertical off the wall about 4".  Finishes are primarily comprised of leafing with palladium, gold, aluminum, silver etc.  They're all lacquered and then waxed.  

(These look best as either single installations, or in multiples of the same finish.)