The S stands for the Mint in Sydney Australia. Your coin is KM# 13 and the mintage is 1,346,000. The reason you are getting conflicting info is there is also a Jubilee head of the same date. I do not know what grade your coin is but since the sovereign you have is neither rare or scarce they sell usually for a little of bullion value and dealers pay a little under bullion value. That being the case the only way to find out how much it is worth is to know what the value of gold is on the day you sell it. A call to a coin dealer will give you the spot price of gold that day. A newspaper will too. I do not know what gold is going for at this time. Hope this helps.