What is the value of a 1939 one ounce fine silver walking liberty silver dollar?

If it the date is 1939 and it says "HALF DOLLAR" on the back then this is not a one-ounce bullion coin; they were first issued in 1986. It's an actual coin that was used in ordinary commerce. Its value is mostly determined by the current price of silver which changes every day. Check a site like kitco or CNNMoney for the current spot price of silver, then multiply by 0.36 for an approximate worth.