Talk about a monumental task. We set out to identify 10 products that have changed the face of jewelry retailing forever, products so iconic—to their makers and their categories—that they've spawned countless iterations, earning honorary membership in the jewelry hall of fame.Naively, we thought the answers would be obvious. And, to some extent, they were—only we didn't anticipate the passion with which everyone offered and defended their choices. Arguments were made. Debates ensued. So we took our questions to a handful of experts. Little surprise—no two people agreed on the same list of 10.The "products" we ended up with include jewels, watches, techniques, and even something as ambiguous as a concept (De Beers' very own game changer, the three-stone ring campaign). The common denominator? All the items are considered so essential to the ­jewelry business today that we take fo