I have found a 1960 D mint coin with an error on the first 's' in United States of America on the back of the coin. How much can this be worth? (these pictures are scanned copies of the coin)
That appears to be a die break on the lower half of the letter "s" of States. Part of the die has chipped away in this area, leaving a depression which subsequently fills with extra metal as each subsequent blank is struck. These are often referred to as "filled" letter or "filled" mint mark "errors." Unfortunately, these are quite common and not worth much of a premium (if any). I can say that it is in a pretty unusual location and I would hold onto it if I found it. I have seen sets put together which trace the progression of certain die breaks over time and those can be really cool!
