วันพฤหัสบดีที่ 23 สิงหาคม พ.ศ. 2550

Other silver standards

Fine silver is 99.9% silver or better. This grade of silver is used to make bullion bars for international commodities trading. In the modern world Fine Silver is understood to be too soft for general use. Britannia silver is purer than sterling, at least 95.84% silver and up to 4.16% copper. Its marks were Britannia and a lion's head in profile. The Britannia standard was a standard of plate obligatory in Britain between 1697 and 1720 to try to help prevent British sterling silver coins from being melted to make plate. It became an optional standard thereafter, and in the United Kingdom and Ireland is now denoted by the millesimal fineness hallmark "958", with the symbol of Britannia being applied optionally. Mexican silver is also purer than sterling, usually 95% Silver and 5% Copper. Mexico is the only country currently using silver in its circulating coinage, but these coins are not minted from 95% "Mexican" Silver. Much of the currently produced silver jewelry and other decorative silver objects made in Mexico at the present time are made according to the Sterling, i.e. 92.5% silver, standard, and are marked "Sterling". Coin silver is most commonly 90% silver and 10% copper as dictated by United States FTC guidelines. "Coin Silver" is said to have acquired its name because much of it was made from melting down silver coins, which are generally of the 90% standard. This does allow for some variation in the silver content, depending on which coinage was used to create the silver stock. Coin silver is usually lower in silver content than sterling. The Coin standard came into common use for table silver in the US during the 1820s, and lasted until 1868. This grade of silver was used in the silver coinage of the US, (until 1964) and also by other countries that minted silver currency , such as Panama and the Philippines. German silver (not to be confused with nickel silver, which is also referred to by this same term) are several silver standards used in Germany. However, the most common standard for silverware and decorative silver objects is the 800 standard (80% pure silver). Hence, when the term German silver is used, it is usually referred to as the 800 standard. Another silver standard in use is the 900 standard. German silver objects are usually marked with an "800" or "900" to show the standard to which they are made. The UK Assay offices also recognise the 80% silver content which is legally represented by the 800 stamp. For industrial uses, for example in electronics, alloys such as copper-silver, CuAg, are favored, which contains 72% silver and 28% copper and is known for its thermal conductivity.