What is the value of a one troy ounce silver coin with no date on it?

It sounds like what you have is a privately minted bullion coin that is meant to look like a US Seated Liberty dollar from the mid 1800's. If it is in fact silver, it is likely worth no more than the metal value of the coin (silver is trading at US$35.30 per troy ounce as of midday on March 4, 2011). If it is not actually silver, it probably has very little value.