I found while swinging an old stagecoach route in AZ, I found what i originally thought was a washer or rivet back. after a closer look, it appears to be a thin 17mm brass/copper coin with a round hole. no designs or images, just characters. 4 on one side, two on the other. see photos, silvery look is sun light on dust. After looking closer, its a Chinese coin. thin brass or copper with round hole in the middle. see photos. anyone out there have a clue what it actually is? thanks see photos. any help in identifying would be appreciated.