The Republic of Palau is an island country in the western Pacific, in free association with the United States. In one way or another, the country has been under US administration since it was established, and has never had its own separate currency - it has always used the US Dollar. However, Palau allows some foreign mints to issue coins under its authority; these are denominated in US Dollars but are only legal tender in Palau, so can in a way be considered to be in "Palau Dollars", even though such a currency does not officially exist.
The coins are usually dedicated to historical or general popular culture themes not related to the country itself. Many of them are in standard bullion sizes, including the large three troy ounces (3oz) of silver format.
The Mint says about this coin:
The Milky Way coin is the second release in the Space; the Final Frontier series.
The Milky Way is one of the many galaxies in the universe. It is the one with our solar system with our planet earth. It is a so called barred spiral galaxy with a diameter of up to 200,000 light-years. Our solar system is approximately 27,000 light-years from the centre. One light-year is 9.46 trillion kilometres.
The Milky Way can be seen as a hazy band of light in the night sky. This is also from which the name is derived: Via Lactea in Latin or Galaktikos Kyklos in Greek which means "milky circle". With the naked eye one cannot see the individual starts but in 1610 Galileo Galilei did. For 300 years it was believed the Milky Way was the whole universe but in the 20th century it was Edwin Hubble who showed it is just one of many.