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Coin cleaning is the controversial process of removing undesirable substances from a coin's surface in order to make it more attractive to potential buyers. The subject is disputed among the numismatic community whether cleaning coins is necessary. Those that argue in favor of cleaning are also in dispute on which methods work best.
Vietnamese cash coins of the 1800s were made of zinc, as was the Vietnamese Tonkin 1/600 piastre of 1905. Zinc was a common metal of choice for American "good-for" tokens . An aluminium token coin from the 1887 American Exhibition in London.
Zinc refining is the process of purifying zinc to special high grade (SHG) zinc, which is at least 99.995% pure. [1] This process is not usually required when smelting of zinc is done through electrolysis processes, but is needed when zinc is produced by pyrometallurgical processes, because it is only 98.5% pure.
It is a form of extractive metallurgy that is used to obtain many metals such as iron, copper, silver, tin, lead and zinc. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal behind.
Toning patterns may cover an entire coin, just one side, or just one area. Coins which have sat stacked in bags for a long time can develop crescent toning, where the toned coin was partially covered by one sitting off-center on top of it. This is common with Morgan dollars, which were typically delivered to and stored in banks in large cloth bags.
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The 2 + 1 ⁄ 2-cent coin minted in the Netherlands during World War II was made of zinc, and worth 1 ⁄ 40, or .025, of the Dutch guilder. It was designed by Nico de Haas , a Dutch national-socialist , and struck in 1941 and 1942.
The zinc 5-cent coin was minted in the Netherlands between 1941 and 1943 during World War II. [1] It was worth 1/20, or .05, of the guilder , and designed by Nico de Haas , a Dutch national-socialist .