The country of Austria recently began pressing 25-euro pieces using niobium and silver in combination. The first section of this article describes some of the recent designs they have used on their coins. The second part describes a bit about the unique manner in which the mint presses these coins.
The earlier versions of the coin, first pressed during the years 2002 and 2003, used titanium for the first two years of the coin's production. The early versions used a re-issue of an image originally printed on an Austrian coin pressed in 1486. The other side pictures a small satellite.
The 2009 version of the coin celebrates Galileo and the 400-year anniversary of the invention of the telescope. The opposite side pictures the dark side of the moon.
The Austrian Mint chose renewable energy as a theme for the 2010 edition of their 25-euro piece. One side of the coin depicts a tree. Emanating from the tree is a spiral image signifying the cycle of life. The opposite side of the coin bears small images representing various types of renewable energy technologies, with the earth situated prominently in the center. The legend to the coin reads "Erneuer bare Energie", which translates from Austrian to English as "renewable energy".
The imagery on the 2011 version of the same niobium silver coins deals with the theme of robotics. It features a robot-shaped human in the splay-legged, splay-armed position of Leonardo Da Vinci's Vetruvian man. The other side of the 2011 edition of the coin depicts the Mars landing, a design pre-figured by the European Space Agency. Formerly known as columbium in the US, Niobium is important in the designs of many alloys used to design spacecraft.
When pressing the coins, the Austrian mint begins with the niobium center, or the "core" of the coin. They oxidize it before pressing it, and then place a silver ring on top of it. The two metals, layered on top of each other are then struck two times in a row. The result of this process is that the two metals melt together along their surface contact. The oxidization also produces a reddish-pink shimmer that you can see from the side of the coin. Each coin fuses together a bit differently during the pressing. As a result, each of them looks slightly different from one another
Austria pressed a total of 65,000 of these coins during the year of 2011. The coin's diameter measures around 34mm, and each coin contains precisely 9 grams of fine silver in the ring portion. This coin will only be issued in "uncirculated" quality and is accompanied by a certificate proving authenticity. The silver used in the coin is 90% pure, a high percentage relative to other silver coins; the niobium is of 99.8% purity.