24-Inch Black Mourning Necklace

This necklace is a little bit of a mystery. It is 24-inches long, with a gold tone ring clasp. There are 1" long oblong beads, alternating with 1/2" round beads, interspersed with tiny cream coasted spacer beads. (The space beads had gold coating, but only traces are left.) It appears to be from the 1930's. I am not sure of the material - probably some sort of plastic (not Bakelite). It looks porous like bone, but there are seam lines in the long beads. N-030