These pearls were passed down generation to generation from at least my great grandmother. They're probably from at least the 1910s or 1920s, but very possibly earlier than that. They definitely pass the tooth test. The biggest pearl is probably 5mm. They have great sentimental value, but I've always been curious about them. Sorry I couldn't get any really good close ups, the pics were really blurry. But, the clasp seems to be sterling and marcasite, I think. Any thoughts?