Art Deco 3 intersecting circles pin brooch 1/20th 12k gold filled signed vintage jewelry ll2156

A classic circle pin times three. Three intersecting circles in graduated sizes are joined at the top by a small disc with three nesting Cs. I assume this is a signature but I don't recognize it. It is marked on the back 1/20 12kf. The pin has a slightly rose gold look in the photos but is yellow gold. It is 1.5 inches and has a safety clasp on the back. Excellent vintage condition. Probably dates to the 1930s.