The 1804 Silver Dollar is a United States dollar coin

United States dollar coin

Dollar coins have been minted in the United States in gold, silver, and base metal versions. The term silver dollar is often used for any large white metal coin issued by the United States with a face value of one dollar, although purists insist that a dollar is not silver unless it contains some...

 considered to be one of the rarest and most famous coins in the world, due to its unique history. Divided into "Classes," 15 specimens are known. Eight comprise Class I, which were minted in 1834. Two Class I specimens trace their lineage to the King of Siam

Jessadabodindra

Phra Bat Somdet Phra Poramintharamaha Jessadabodindra Phra Nangklao Chao Yu Hua , or Rama III , was the third monarch of Siam under the House of Chakri, ruling from 21 July 1824 to 2 April 1851. He succeeded his father, Buddha Loetla Nabhalai, as the King of Siam...

 and the Sultan of Muscat

Said bin Sultan, Sultan of Muscat and Oman

Said bin Sultan Al-Said was Sultan of Muscat and Oman from November 20, 1804 to June 4, 1856. He became joint ruler of the country along with his brother Salim on the death of their father, Sultan bin Ahmad, in 1804...

. One comprises Class II and six comprise Class III and were minted sometime between 1858 to 1860.