New York’s Tiffany & Co. was founded in 1837. The company began modestly as a stationary store. Then, in 1848, a trip to Paris by one of the firm’s founders netted a huge cache of diamonds, which were being unloaded at fire-sale prices by nobles fleeing France’s second revolution. From then on, diamonds remained a key jewel in the Tiffany crown.

Tiffany did not cater just to high rollers. In 1858, the company produced and sold pendants made out of surplus cable from the first transatlantic phone lines—customers could pick up one of these souvenirs for a mere 50 cents. But in the main, Tiffany became increasingly associated with fine jewelry for high-profile clients, such as the seed-pearl pieces the company designed for Mary Todd Lincoln to be worn at her husband’s 1861 inauguration.

By 1886, Tiffany had introduced rings with the famous Tiffany Setting. Simplicity itself, it consisted of a single diamond anchored to a plain band by six exposed prongs. As the 19th century waned, Tiffany was producing pieces with Japanese motifs, diamond necklaces in the Edwardian garland style, and Paulding Farnham-designed flower brooches that were almost-life-size—a bearded iris pin, whose flower dripped with blue Montana sapphires and red rhodolites and whose stem was studded with green garnets, measured 9 1/2 inches...