I don't question its authenticity or the nature of the toning. Looks natural to me. As far as the slab, I would just doubt the grade. At least it's giving it some protection, or you could break it out and put it in a capsule.
In Memory of Crazyb0 12-26-1951 to 7-27-2020
In Memory of Tootallious 3-31-1964 to 4-15-2020
Oh that I was where I would be,
Then I would be where I am not,
Here I am where I must be,
Go where I would, I can not.