This is a very nice vintage sterling silver butterfly-abalone shell necklace (assumed to be abalone shell, based on appearance). The butterfly is composed of three pieces of abalone shell; each wing appears to be a single piece of shell and the butterfly body is also a single piece of abalone shell.
It was purchased new many years ago; from memory we believe it would have been in the early 1970's. It has been mostly in storage for the past 30 years. The mark on the back of the butterfly shows incomplete lettering; the clasp is clearly marked sterling.
The sterling silver shows a typical shiny dark patina, even after polishing with a silver polishing cloth.
Necklace: length = 16 inches, weight = 2.9 grams
Width across widest tip of wings: approximately 25 mm.
Length from top of antennae to wing tip: approximately 25 mm.