Louis XVIII, known as the Desired, was King of France from 1814 to 1824, except for the Hundred Days in 1815. He spent twenty-three years in exile: during the French Revolution and the First French Empire, and during the Hundred Days. This gilded commemorative medal, (likely bronze with layer of gold, since there are no French silver marks) is of that "Restauration" King Louis XIII (b. 1755, d 1824, Louvre Palace). You'll want to read the history. I am uncertain if this commemorated his death (1824), or comes within 20-50 years afterward. More research. Full measurements noted on the photos.
Very good to excellent condition for age and type, there is really just a little surface abrasion here or there, and a fine hairline on one side of the bottom half, which I marked with an X for your review. Light in weight, but not tortoiseshell, I feel certain it is either exceptionally thin lathe-turned ebony, or a cast material. If a 'gold anniversary' commemorative of his rule, start or finish, it would be Napoleon III era and therefore can be a composition. Napoleon III, France's last Emperor, was gone, though, by 1870s, and it seems most likely a 50-year commemorative of Louis XVIII's coronation, so 1864.
