An oval copper plate, and two whatsits

These items were all found at really old house sites. The oval copper plate actually has holes at each "corner" that I hope the pictures somewhat show. The thing with the teeth is iron and is much too thick and the teeth too far spaced apart for it to be a saw piece. I was thinking a brake adjustment for a wagon? But I haven't got a clue. The third piece rang up as iron and it looks like some type of lock cover, but wasn't sure and I thought some of you might have some ideas. Thanks for your help and HH.