Why is it called a "jewel case" anyway?

According to wikipedia:

"The case does not derive in any way from containers for jewelry. Instead, the name apparently originates from watchmakers' use of the term jewel to refer generally to a polished hemispherical bearing used in a mechanism (high-quality mechanical watches and clocks commonly use gemstones, typically rubies, for such bearings because of their low friction properties). A jewel case has two moulded hemispherical plastic bearings, in its hinges, hence the use of the term 'jewel'."

[via wikipedia]