Again, just enough energy for one post today.
I agree with Randywa and Fyrffytr1 on the first 3 items:
1 - a brass or copper rivet from a leather object (such as, a horseharness bridle or saddlebag, etc.),
2 - a farming-equipment cultivator tooth,
3 - a very-bent horseharness rein-guide (a.k.a. "terret").
Number 4 appears to be the broken off rear part of an ax blade (broken through where the wooden handle goes through the ax's blade).