The Caroline Islands are a large archipelago of small islands forming a chain of many small islands in the western Pacific Ocean, northeast of Papua. They are presently divided between the Federated States of Micronesia in the eastern part of the chain, and Palau in the western end.
Most of the islands are low, flat coral reefs, but some are [[mountain]ous.
The first European visit to the islands was by the Spanish in 1543, and originally named after Charles V, Holy Roman Emperor.
The Spanish did not occupy any island formally until 1886, and then after the Spanish-American War, in 1899, they sold the islands to Germany. Japan occupied the islands in 1914 and received a mandate over them in 1920, but after World War II the islands became trust territories of the United States, eventually becoming independent.
In their first year as a German possession, the Carolines used postage stamps of Germany overprinted "Karolinen", which are today uncommon, especially used. In 1901, Germany issued its "Yacht" series, a common design for all of Germany's colonies, featuring the Kaiser's yacht Hohenzollern. The issues for the Carolines were inscribed "KAROLINEN", all with pfennig and mark denominations. Unused copies of the low values are common today, there being many left over after the Japanese occupation, but as might be expected from the short period of rule and the very small numbers of letter writers living in the Carolines, genuinely used stamps are both uncommon and prized.
(should add a picture of a stamp)