One interesting feature of the American Platinum Eagle coin is that its reverse design changes every year. The Canadian Platinum Maple Leaf: The Canadian Platinum Maple Leaf bullion coins were issued from 1988 until 2002 by the Royal Canadian Mint (RCM). They were offered in four varieties: 1/10 oz. coin (with a face value (FV) of CD5), 1/4 oz. The high-ductility property of gold and silver means they can be easily damaged as coins for circulation. Coins intended for circulation must be highly resistant to corrosion and wear. For this reason, gold or silver must be alloyed with other metals (example, manganese) so that the resulting coins will come out harder, more wear-resistant, and not easily damaged or deformed. The principal sources of silver are copper, lead, zinc and gold ores. It also occurs in the minerals chlorargyrite and argentite. Of course, silver occurs natively, too. Some of the top silver-producing countries in the world are the United States, Canada, Peru, and Mexico. Fine silver, which has no less than 99.9% silver, is available commercially. Iridium is found at highest concentrations within the Earth's crust in three specific types of geologic structures: in impact craters, in igneous deposits, and in deposits reworked from either of the first two. The Bushveld igneous complex in South Africa is the largest known primary reserves for iridium in the world. Of these four, gold is the most popular. Investing in gold is a way of protecting against crises that may be brought about by economic or political instability or by social unrest. There are at least six ways of investing in gold: Buying gold coins: This is the most popular way of investing in gold. Gold bullion coins are typically priced based on their weight; a premium is added to the gold spot price. This composition was meant to make the coins more durable and harder and thus resist dents and scratches, as, again, they were originally intended for circulation. On the obverse of the Krugerrand is the face of Stephanus Jonannes Paulus Kruger, fifth president of the South African Republic (note the surname Kruger and the South African currency Rand were combined to give this precious metal coin its name).