oregon trail

I found this on Mount Hood on the Oregon Trail about a mile hike in or so was waving my detector this thing was easy to pull out of the ground it is used to pull a hourse with a strap through it looks like it broke off what is this puppy called ? any idea if it is worth anything it is brass not...

Alright this just might seem silly to even ask.. But i am new to searching anything other than beaches.. From my understanding here in Idaho you can metal detect and gold pan on BLM public lands.. The Oregon Trail runs all around the area I live mainly on BLM. Would a person be able to metal...