Unzen is German for ounces (unze is the singular). These are large pure silver medals issued by Switzerland for investors. Their value goes up and down with the price of silver. There are many different patterns.
Bullion investing has become popular recently as world currencies rely more and more on unreliable governments. Hard assets such as gold and silver have appeal to investors. We recommend you read our article on gold and silver investing. There are several important topics you should understand about this subject.
To evaluate your 'unzen' coin, multiply its silver content by the current price of silver. Silver content is measured in troy ounces, not avoirdupois ounces, and there are 31.1 grams in one troy ounce. A coin marked '5 unzen' contains 5 troy ounces of silver, or 155.5 grams. Be sure the coin is issued by a reliable government so you can be sure it really contains the amount marked. Also, if the coin is gold, be sure it is solid gold and not simply gold plated.
At the time of this writing, silver is trading around $20 US dollars per troy ounce. The price of silver changes every day, so be sure to look it up on web sites such as kitco.com. The value of a 5 unzen coin is then 5 x 20 = $100 US dollars.
The fact that a bullion coin has proof finishes, or that is has nice packaging, or that it has a certificate of authenticity, are all meaningless. The only thing that contributes to value is silver content. Dealers will usually buy silver coins 10 to 20 percent behind the current price of silver, and they will sell them 10 to 20 percent ahead of the current price of silver.