Joseph was sold for 20 pieces of silver, the unit of monetary value at the time for silver was the Shekel (silver, 0.403oz) ounces did not exist at the time. But the modern equivalent is 8.06 oz of silver. That is equal to $216.25 with silver at $26.83 per ounce today.
This is a bullion coin sold for its silver value, currently about $17/oz. The "$1" denomination is artificial.
The value of silver is constantly changing. Today, 5/11/2012, the value of silver per oz is USD 28.25-28.45.
Your coin is a bullion piece sold for its silver value. It fluctuates with the price of 1 oz of pure silver, around $18 as of 07/2008.
This is a bullion coin sold for its metal value. Silver is currently trading at about $14/oz.
The intrinsic value is $14.16 with silver at $18.31 per ounce. With silver at $47/oz, the silver value is $36.36.!!
The coin isn't actually a dollar. It's a "silver eagle" containing 1 oz of pure silver and sold to collectors and investors. The $1 denomination is artificial. Its actual value changes with the price of silver bullion; as of 02/2010 it sells for about $17-18.
The value changes daily as the market price for silver fluctuates. As of 20 October 2012, silver is worth $32.06/oz, making a 5 oz. bar worth $160.30.
$18
5,393,005 were minted and sold.
The value changes as market prices fluctuate. As of 20 October 2012, silver is worth $32.06/oz, so a 10 oz. silver bar is worth $320.60.
What you have is a silver bullion coin. It may have some value to those who collect such things but basically its value is just the silver it may contain. As of April 24, 2010 that value is $18.28 USD.
The $1 denomination is artificial. You have a bullion piece sold for its silver content; the current price is about $18/oz.