Grandmother's Vintage Costume Jewelry (60s, 70s)

Bright yellow gold with "diamonds" all the way around. 3 grey stones. There is some discoloration by the hook and a little more throughout the necklace, but it's old, sooo I tried cleaning with my jewelry wipe, but it could use a professional cleaning. Not sure on metal but doubt it's actual gold. No markings at all on the necklace. Review pics please.