Well, if you can't find the REAL name for these, you could call them bull nose rings! Who knows, that might even be what they are.

Nose rings are used initially to wean the calves -- they interfere with nursing. Later they are used to control the animals. Other animals also are fitted with the rings.

Usually they have mushroom-shaped rings, but a local blacksmith might have come up with his own design.

Not nose rings.

Part of a harness or wagon, I think.

It looks like the "clevis" that holds the "tree" part where you hook the traces to the rest of the wagon. Some are flat, like this, and some have the end loops at 90 degrees to the ring.

There are several spots on harness where you need a place that a ring can pivot, too, or you need to hold a strap or chain out of the way.

I also think it's likely it's rings for horse leathers.