For your consideration is this wonderful circa 1930s necklace. The yellow beads have passed the simichrome test and I believe the light ivory in color beads are celluloid. It has a nice geometric look and is a very cool piece of old jewelry. The clasp has a metal screw on the inside that screws in securely.
The necklace measures 16 and 1/2 inches when clasped. The center bead is 18.5 mms wide.