I want to say ive seen something like this before and it has to do with horse tack. perhaps goes across the chest? also included are insitu photos, not a bad day when you dont have to dig.
It is a Civil War & Indian Wars era US Cavalry carbine sling belt's tip. Most diggers call it a carbine sling "batwing." The four rivets held it onto the sling-belt's end to keep the leather from fraying and for ease of feeding the belt's end through the carbine sling's buckle.