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2. United States Mint coin sizes - Wikipedia

   en.wikipedia.org/wiki/United_States_Mint_coin_sizes

   US Coin Sizes and Composition Steel Alloy Copper Copper Alloy Silver Alloy Silver Gold Platinum Palladium Three Cent 14 mm 0.8 g 0.750 fine 1851–1853 14 mm 0.75 g 0.900 fine 1854–1873 Half Dime 15.5 mm 1.24 g 1794–1873 Dollar 15 mm 1.67 gr 1849–1889 $5 American Gold Eagle 16.5 mm 3.11 g 1986–present $10 American Platinum Eagle 16.5 mm ...

3. Fineness - Wikipedia

   en.wikipedia.org/wiki/Fineness

   For example, knowing that standard 18-carat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm 3 for gold, 10.49 g/cm 3 for silver and 8.96 g/cm 3 for copper.

4. Coinage metals - Wikipedia

   en.wikipedia.org/wiki/Coinage_metals

   Pre-1992 British pennies were made of 97% copper; but as of 2008, based on the price of copper, the value of a penny from this period is 1.5 new-pence. Modern British pennies are now made of copper-plated steel. Cupronickel, a base metal alloy with varying proportions of copper and nickel, was introduced as a cheaper alternative for silver in ...

5. Gold plating - Wikipedia

   en.wikipedia.org/wiki/Gold_plating

   Gold plated - gold layer thickness greater than or equal to 0.5 micron; Heavy gold plated / Vermeil - gold layer thickness greater than or equal to 2.5 micron; Gold plated silver jewellery can still tarnish as the silver atoms diffuse into the gold layer, causing slow gradual fading of its color and eventually causing tarnishing of the surface ...

6. Carat (mass) - Wikipedia

   en.wikipedia.org/wiki/Carat_(mass)

   Gold fineness in carats comes from carats and grains of gold in a solidus of coin. The conversion rates 1 solidus = 24 carats, 1 carat = 4 grains still stand. [ 16 ] Woolhouse's Measures, Weights and Moneys of All Nations [ 17 ] gives gold fineness in carats of 4 grains, and silver in troy pounds [ 17 ] of 12 troy ounces of 20 pennyweight each.

7. Copper electroplating - Wikipedia

   en.wikipedia.org/wiki/Copper_electroplating

   While copper may be used as the final decorative surface layer, it is usually subsequently plated with other metals that are more resistant to wear or tarnish such as chromium, nickel, or gold; in this case, the brightness of the copper undercoat enhances the appearance of the subsequent finish layer. [5]