The photos are way over pixelated. Is it Zinc or copper? Is it a large date or a small date? There is also some damage in the area, could be damaged.
Just trying to be helpful. When using a cell phn. Do not expand the image before you shoot the photo. Get as close as you can to the coin on 1X before it blurs and then set your lighting. Crop the photo and post in full size. Any magnification will cause the phone to add pixels.
I think that I take pretty decent Pics. Please try this. If not tall enough (too blurry), just increase height of books or whatever you're using.
Using both photos it appears it’s not a D over D mint mark but a case of split plate doubling as explained by @expat.