Has any research been done re the clasps on necklaces ? In my collection I have barrel clasps, one of which Jean Rousselet recently, and most kindly confirmed, is indeed on a Rousselet necklace from the 1920s, informing me that the Paris shop still have some of the same old beads in their archives. I also have Venetian wedding cakes circa 1950s with a distinctive clasp. . Hoping to learn more.