Vintage Brass Tone and Abalone Shell Triangular Necklace

this necklace is a stunner brass tone metal and abalone graduated triangular shapes create this eye-catching piece there is a mark on the hook clasp that I think says alpaca, but it's difficult to make out and in an awkward spot beautiful abalone with flashes of green, blue and purple measurements: diameter ~ approx 5.75" circumference (length) ~ approx 18" in great vintage condition ~ I have cleaned this necklace, but I didn't polish it too vigorously as I know some like the look of the patina