Could be the disc like marker/guide from a seed planter. Attached to an arm that swings up and down on the planter. Just a guess. The 3rd. item is definitely as others stated a chunk of melted metal from being in hot fire for a period of time. I have one nice corner lot across the street from my church and belonging to the church where a house once stood and burned years ago where I have dug up dozens of those in various sizes and shapes. They come in as high tones and generally read dime/quarter range, very annoying and heavy too. Have found them in other sites too.