This Thompson Center manufactured first variation brass buttplate screw with a dome shaped head and full length threads measures between 1.015" and 1.065" in length and is for the Seneca muzzle loading rifle. This brass screw is in very good condition with a light tarnish and honest wear. (file photo)

Note: Thompson Center Seneca muzzle loading rifles with the following serial numbers have been observed with this part: 16559 & 52191