ornamental piece of jade several
瑄 is a rare kanji referring to an ornamental piece of jade. Its meaning is narrow and concrete, with no clear abstract extensions.
瑄 combines 王 (jade) with 宣, which likely contributes the sound. The exact historical development is uncertain.
The left side 王 (jade) tells you it's a type of jade. The right side 宣 looks like a decorative stand, so imagine an ornamental jade piece displayed on a stand.
For セン, picture a sen coin (銭) made of jade: sen -> セン, and this ornamental jade piece is as valuable as a hundred sen.