It is worth whatever one troy pound of silver is worth. Since 1 troy pound is 12 troy ounces and since one troy ounce of silver is worth ~$22, your coin is worth $264. However, keep in mind that silver prices fluctuate on a minute by minute basis.
Sorry but no U.S. coins dated 1958 weigh "One Troy Ounce". Look at the coin again an post new question.
This coin 2010 is worth between .45-50.00
The value of a troy ounce coin of 999 fine silver is based on the current spot price of silver in the market. You can calculate its worth by multiplying the weight of the coin in troy ounces by the current spot price of silver. Additionally, consider any premiums or fees that may apply when buying or selling the coin.
The current spot price of silver is about $43 per troy ounce.
The value is just for the silver, about $28.00
550-600
A troy ounce is about 31 grams and the US standard ounce (avoirdupois) is about 28 grams. When buying coins, or gold or silver, you get more by getting a troy ounce. The price of gold and silver is in troy ounces. So, for example, if gold is $1400 an ounce, that price is for a troy ounce. A 28 gram ounce of gold is not worth $1400.
As of 21 July 2016, it would be worth just shy of $40.
At today's rate, it is worth $43.40.
What does it say on it? Most modern bullion coins will give the weight of the gold in the coin in troy ounces on the coin somewhere. If your coin has that, it is rather easy to find your coin's value, just simply find the value of gold in troy ounces that day and figure out how much your coin is worth from that. If your coin doesn't have a weight listed, it should have identifiable characteristics such as the year, design, country of origin, and other ways to identify your coin. Without knowing the details about your coin it is impossible to truly answer your question.
Those coins likely are never going to be worth more than their weight in silver...2 troy ounces... http://lmgtfy.com/?q=how+much+is+2+troy+ounces+of+silver+worth