This one is easy. It isn't often that a country has decided to use a pure metal for coinage. Typically silver coins have some copper and copper ones some tin. Even gold coinage meant for circulation used to be alloyed with a little copper to help it wear better. The sole prominent exception has been the Canadian nickel which for many years had been made with pure nickel. Nothing wrong with the choice, it's an excellent metal for coinage in the sense that its exceptional hardness meant that it would last in circulation for many years. But that hardness was also hell on the dies which wore out much more quickly than they did when coining softer metals. And then also nickel, even in a major producer like Canada, was never the cheapest of metals. It was curtains for nickel in 1981 and now their nickel is but skin deep with a worthless ferrous heart.

CAS 7440-02-0