Send a message to the person who requested a photo of the grave monument of Duncan Maclean with the following comment:
I believe this is the gravestone of my Great, Great. Great grandfather, Duncan McLean, father of Roderick, father of John, father of Addis Albro, my grandfather. :) I am extremely grateful for your work. Even if this somehow turns out to not be the right one, I am encouraged by and appreciate your effort!