Silver coins have evolved in many different forms through the ages; a rough timeline for silver coins is as follows:
▪ Silver coins circulated widely as money in Europe and later the Americas from before the time of Alexander the Great until the 1960s.
▪ 16th – 19th centuries: World silver crowns, the most famous is arguably the Mexican 8 reales (also known as Spanish dollar), minted in many different parts of the world to facilitate trade. Size is more or less standardized at around 38mm with many minor variations in weight and sizes among different issuing nations. Declining towards the end of the 19th century due the introduction of secure printing of paper currency. It is no longer convenient to carry sacks of silver coins when they can be deposited in the bank for a certificate of deposit carrying the same value. Smaller denominations exist to complement currency usability by the public.
▪ 1870s – 1930s: Silver trade dollars, a world standard of its era in weight and purity following the example of the older Mexican 8 Reales to facilitate trade in the Far East. Examples: French Indochina Piastres, British Trade Dollar, US Trade Dollar, Japanese 1 Yen, Chinese 1 Dollar. Smaller denomination exists to complement currency usability by the public.
▪ 1930s – 1960s: Alloyed in circulating coins of many different governments of the world. This period ended when it was no longer economical for world governments to keep silver as an alloying element in their circulating coins.
▪ 1960s – current: Modern crown sized commemoratives, using the weight and size of the old world crowns.
▪ 1980 – current: Modern silver bullion coins, mainly from 39mm – 42mm diameter, containing 1 troy ounce of pure silver in content, regardless of purity. Smaller and bigger sizes exist mainly to complement the collectible set for numismatics market. Some are also purchased as a mean for the masses to buy a standardized store of value, which in this case is silver.
Article Source: en.wikipedia.org