Jewelry collectors tend to go gaga over venerable brand names. But for true connoisseurs, intrinsic value always trumps labels. Take this exquisite rose gold colored diamond ring, which is unsigned and has no known maker, yet earned more than $3.5 million at auction. Daphne Lingon, senior vice president and senior specialist for Christie’s, which sold the ring on May 27 in Hong Kong, says the center stone—a 6.13 ct. fancy intense green diamond with strong color saturation—was what lured the big spenders: “Green is one of the rarest colors in which to find naturally occurring ­diamonds—following red, and ahead of even blue and orange. A naturally colored green diamond is a true rarity of nature.” She estimates the ring was made within the past 10 years, and is sure its fabricator was “someone with an understanding of rare colored diamonds.”