Old antique heavy cast brass architectural or early industrial door knob. This door knob has a threaded and knurled base. The base is nicely stamped with a US patent date in 1908. The knob measures about 2 1/8" across and 2 1/8" long. This appears to have originally been made to mount on a regular threaded screw, but has been hand modified to accept a square shank (about 5/16" across).