1900's vintage harvested pearl and amethyst neckla

I had a basic appraisal done on this piece: Very lovely early 1900s (1910-20) necklace in silver I think, decorated with ametyst and oriental pearls. A market valuation is approx. $500. I was advised by the appraiser to clean with a light silver cloth but both agreed the patina is quite charming (and helped narrow down the appraisal) so I have not removed. Chain is 18" and original. The clasp is quite unique and also helped in the dating of the piece.