This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 珡 is uncertain. It visually contains 玨 (two pieces of jade) on top, but the lower component is unclear.
The top part 玨 looks like two pieces of jade. Without a clear meaning, picture a mysterious ancient artifact made of paired jade pieces.
For キン, imagine a king (キン) inspecting the mysterious jade artifact: king -> キン, and the jade pieces gleam under his gaze.