Did you have another question besides the one you asked? Filled Mint Mark is what I also see.. Known as a Die Chip Nothing really major
The coin posted is a San Francisco coin, not a Denver coin. I understand what the OP is asking and to that I say No, not a S/D, but truthfully I can see where you might get that idea. The S Mint Mark punch was replaced mid year for a clearer S. Some 1979 proofs have the clear S, but it would not be used for circulation strikes until 1980.