Unusual Coins

The Royal Canadian Mint is now able to produce holographic-effect gold and silver coinage. However this procedure is not limited to only bullion or commemorative coinage. The 500 yen coin from Japan, was subject to a massive amount of counterfeiting. The Japanese government in response produced a circulatory coin with a holographic image.
The Canadian Mint has also released several coins that are coloured, the first of which was in commemoration of remembrance day. The subject was a coloured poppy on the reverse of a 25 cent piece.
For a list of many pure metallic elements and their alloys which have been used in actual circulation coins and for trial experiments.
Coins are popularly used as a sort of two-sided die; in order to choose between two options with a random possibility, one choice will be labeled "heads" and the other "tails", and a coin will be flipped or "tossed" to see whether the heads or tails side comes up on top. A fair coin is defined to have the probability of heads (in the parlance of Bernoulli trials, a "success") of exactly 0.5. Coins are sometimes falsified to make one side weigh more, in order to simulate a fair type of coin which is actually not fair. Such a coin is said to be "weighted".