I bought this set of pearls at a thrift store. I have been researching the maker's mark, and what kind of pearls these are, but I'm stumped. The pearls are gritty and cool to the touch, and measure 4 mm, 17 in. necklace, and 7 in. bracelet. The clasp has 10k and a stamp marked on both pieces, and 10K is stamped on the circle part of the clasp, too. Any information would be helpful. Thank you!