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I agree with our Good Friend of Volunteer Origin - Juglans nigra indeed.
I would ask RoscoeJJ:
Have you taken a whiff of the foliage, bark/wood, and/or the seeds/husk of the plant in question? If you know what Black Walnut smells like, this will always tell you. If you don't know (yet), now you always will. You won't need leaves or seeds in the future.
Thanks guys, my next question is when to remove the husk? As you can see, I tried one of them but, it took a knife to do so. And it's tough to remove the husk entirely at this stage. So, shall I leave them as they are in the picture for a certain period of time before de-husking? How shall I proceed?
Typically, with time the exteriors start turning dark brown to black - at which point they are much easier to husk. I think you may have harvested that batch a bit early, unless they had already dropped at that stage. A couple weeks outdoors ought to do the trick (protected from foragers, of course).