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 the Gotthard Mail Coach (German: Gotthardpost; Frennch: Diligence du Gothard).
Swissmint says about it:
For many years, the Schöllenen gorge formed an insurmountable barrier on the route over the Gotthard Pass. The opening-up of the Schöllenen gorge by means of the Twärrenbrücke bridge - a walkway alongside the vertical cliff face - as well as the construction of the first wooden bridge over the River Reuss (known as The Devil's Bridge) and the two to three metre wide mule track surfaced with gravel and granite slabs helped the Gotthard Pass enjoy a rapid boom in the 13th century. Since its creation, the old mule track dating from the Middle Ages had been gradually improved so that by the end of the 18th century, sections were also passable by the Gotthard mail coaches.
In 1830, the new Gotthard road was opened and by 1831 as many as 900 mail coaches rolled over the pass. A regular service operated three times a week in each direction between Flüelen and Chiasso using small one-horse carriages with two or three seats. The heyday of the Gotthard mail coaches only began in 1842 however with the introduction of a daily five horse, ten-seat coach in each direction. The journey from Como to Flüelen took almost 23 hours. Whereas there were still only two mail coach connections a week in 1835, from 1849 a twice daily service was already in operation. With the opening of the Gotthard railway in 1882, the Gotthard mail coaches lost importance overnight. From then on, travellers and goods were conveyed by rail through the newly constructed Gotthard tunnel, dispensing with the need for the arduous and hazardous journeys over the pass.