A mysterious pearl necklace that may have once belonged to Catherine the Great, Empress of Russia, will be auctioned off by Bonhams in New York in December. Automotive billionaire Horace Elgin Dodge purchased the necklace from Cartier in Paris in 1920 for his wife Anna Thomson Dodge at the astonishing price of $825,000 - about $8 million in today's dollars.

The original Cartier invoice states that the "five row pearl necklace, consisting of 389 pearls weighing 4305 grains" was accompanied by an "enamel clasp representing Catherine, Empress of Russia" and "two diamond alternate clasps." Several newspaper accounts from the '20s suggested that the pearls did indeed once belong to Catherine; Anna Thomson Dodge's heirs maintain that Horace bought the pearls from Cartier on that basis.

Now reduced to three strands comprised of 224 pearls and two Cartier diamond clasps, the necklace (above) is estimated at $500,000- $700,000 - a hefty sum, to be sure, but far less than Horace originally paid. The reason for the depreciation has less to do with the reduction in strands than with changing fashion and an evolving jewelry marketplace.

In 1920, before the advent of cultured pearls, they were exceedingly rare and valuable, much more so than diamonds. Nowadays pearls have become more commonplace while diamonds are more precious, though a true connoisseur recognizes the value of the Dodge necklace, which is made of all natural pearls.