The Royal Australian Mint has released the 2012 Crux Southern Sky $5 Silver Proof Coin. This new release is dome shaped, representing a first for the RAM.
The Crux constellation, also known as the “Southern Cross,” is one of the smallest of the 88 modern constellations, but one of the most distinctive. It is easily visible in the southern hemisphere night sky at practically any time of year and made up of five stars. The four main stars form a cross, from which it takes its name.
The reverse design of the coin is color printed on a concave surface, which should provide a dramatic display of the constellation framed within a compass border. The obverse is convex and includes a portrait of Queen Elizabeth II.
Each coin is struck in 99.9% silver with a weight of 1 oz and diameter of 39.62 mm. The coins are packaged in a presentation tin with an insert that allows the coin to be displayed upright.
The product page can be found here. The price for international orders is AUD$100.00.
While this is a first for the Royal Australian Mint, the format of a dome shaped coin has been used before. The Monnaie de Paris issued the 2009 International Year of Astronomy Coin, which I believe won a Coin of the Year Award.
The United States Mint may issue a dome shaped commemorative coins for the baseball hall of fame. A bill passed by both the Senate and House of Representatives calls for the reverse of the silver dollar and $5 gold coins to be convex to closely resemble a baseball and for the obverse to be concave for dramatic display of the design. This format is not required, but recommended as sense of the Congress and “to the extent possible without significantly adding to the purchase price of the coins.”