The Fifty Francs coin is a denomination of the Swiss Franc. Given that Switzerland has four official languages, the Franc has three different names: Franken in German, franc in French and Romansh, and franco in Italian.
In regular circulation, the denomination is served by a banknote. These gold coins are non-circulating legal tender made for collectors and struck in proof grade only. They are issued in topical series, celebrating various aspects of Swiss heritage or nature. Swissmint has issued at least one every year since 2001. Initially, both sides of the coin carried a commemorative design; starting from 2004, the obverse is the same and only the reverse changes. (It is worth mentioning that some sources consider it the other way round, and call the commemorative part the obverse; however, we are going with the standard definition, which is that "obverse" is the side which specifies the issuing authority).
The edge is inscribed with the motto DOMINUS PROVIDEBIT (The Lord will provide - a quote from the Bible, Genesis 22, 8), and thirteen stars representing the original thirteen cantons of the Swiss Federation.
This coin commemorates Heidi - a work of children's fiction published in 1881 by Swiss author Johanna Spyri. It was originally published in two parts as Heidi: Her Years of Wandering and Learning (German: Heidis Lehr- und Wanderjahre) and Heidi: How She Used What She Learned (German: Heidi kann brauchen, was es gelernt hat).
It is a novel about the events in the life of a 5-year-old girl in her paternal grandfather's care in the Swiss Alps. It was written as a book "for children and those who love children" (as quoted from its subtitle). Heidi is one of the best-selling books ever written and is among the best-known works of Swiss literature.
This coin is the first 50 Francs commemorative gold coin issued by Switzerland. | 
Search for Switzerland: Fifty Francs 2001 Heidi on eBay 