Send a message to the person who requested a photo of the grave monument of Mary Siddall with the following comment:
I believe this could be the grave of my 5x great grandmother, though the birth date must be wrong. She was born in 1753, married her first husband in 1779 and John Siddall in 1790. Alternatively, the John in the grave could be her daughter-in-law. I'm anxious to clarify the problem.