WIKIPEDIA:

“ A gold medal is typically the medal awarded for highest achievement in a non-military field. Its name derives from the use of at least a fraction of gold in form of plating or alloying in its manufacture. The award concept arose in the military, initially by simple recognition of military rank, and later by decorations for admission to military orders dating back to medieval times.
Since the eighteenth century, gold medals have been awarded in the arts, for example, by the Royal Danish Academy, usually as a symbol of an award to give an outstanding student some financial freedom. Others offer only the prestige of the award. Many organizations now award gold medals either annually or extraordinarily, including UNESCO and various academic societies.
While most gold medals are solid gold, notable exceptions are gold-plated and often silver-gilt, like those of the Olympic Games, the Lorentz Medal, the United States Congressional Gold Medal (displayed to the right) and the Nobel Prize medal. Nobel Prize medals consist of 18 carat green gold plated with 24 carat gold. Before 1980 they were struck in 23 carat gold.

Military origins
Before the establishment of standard military awards, e.g., the Medal of Honor, it was common practice to have [......] ”

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