Napoleon had jeweler Alexandre-Gabriel Lemonnier (circa 1808-1884) make this piece c. 1850. In the Louis XVI style, a filigree silver-gilt mount is over crusted with 1998 small diamonds. They surround much larger pearls, and give them absolute priority. The largest drop-shaped pearl in the top-most position is believed to be the “Perle Napoleon”
Here is Empress Eugenie wearing it.