What is this?

[Rdh5832]

Hi guys. I live on missionary ridge in Chattanooga TN where a lot of battles took place. I metal detected my yard over the past couple days and found a few things. No idea what they are. I do believe the one photo is a railroad spike. Any feedback would be greatly appreciated. Thanks

 

[fyrffytr1]

The square piece is a nut. It most likely came from a fishplate. The fishplate was used to join two sections of rail together. You can see your nut in the picture below. I am not sure about the other two items but my gut feeling is they are 20th century.