It looks like some dirt or corrosion on the D and maybe even a little damage under the dirt. I don't see as S under the D and as spruett001 said, there are no 1959 D over S mint mark cents listed.
Keep looking!
ANA ID: 3203813 - CONECA ID: N-5637 Clean a coin that may be worth collecting? Please DON'T! When in doubt, leave it dirty!!
























