This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
銗 combines 金 (metal) with 后, but the exact historical development and original meaning are uncertain.
The left side is metal 金, and the right side is 后. Without a clear meaning, picture a metal object associated with a ruler or empress (后), but its purpose is unknown.
For コウ, imagine a metal collar (くびかせ) worn by a court official (公, コウ) in ancient times: 公 -> コウ, and the metal 金 collar is the 銗.