precious stone
璢 centers on a precious stone or gem, a rare and valuable mineral substance.
璢 combines 王 (jade/precious stone) with 畱, which likely contributes the sound. The exact historical development of 畱 is uncertain, but the character is a phono-semantic compound for a type of gem.
The left side 王 (jade) signals a precious stone, and the right side 畱 looks like a complex, ornate setting holding the gem in place.
For ル, imagine a precious stone shaped like a small room key: the key's shape cues ル (ru), and the stone is so valuable it unlocks a treasure room.