Thanks. The reason I didn't think it was wear was, the d is raised good. It's easier to see in person.
Think just a moment what the inside of the "D" is, on the die instead of the coin. It's a tiny little piece of die steel sticking UP with the letter being a recessed "moat" around it. Now, how easy might it be for some random mechanical accident to shear off that little peak? Pretty easy. It's why filled mintmarks are no big deal. It's amazing we don't see it more.
Don't forget, every coin struck from that particular die will have the die chip/blob. There are more of them out there than there are interested collectors. I call them 'interesting conversation pieces', and they are errors, but minor and fairly easily found. good eye to spot it.
Many filled in mint marks. Weak. Half missing. Grease filled. Some of the damaged parts of earlier coinage