Help identifying mark sideways M inside of C sterling earrings

[syboni]

I have had these earrings for over 30 years. Searched many books and online for the mark and haven't found anything. I see the letter M, sideways, inside the letter C, and possibly the letter L. The ivory or cream-colored piece is not plastic, it is glass or something. They are a great design and it would be great to know who designed them. American? Scandinavian? I appreciate your help!