I'm glad you found the Atchinson research of interest. My grandfather was George Keeble the brother of Lancelot and grandson of William Atchinson. George's son Richard was my father.
I knew about the locket inscribed for Marian from my mother. There is one puzzle as on the 1911 census Elizabeth Atchinson says she had 7 children, 3 of whom died. I can only account for 6. The children who survived - Frank(1855), Charles (56),Gilbert (62) and Laura(63) and the 2 who died as infants Marian (57) and Annie Louisa (59). I wondered if a child was born after Laura's birth and before Elizabeth and William separated in 1870.
I wonder if you have any family lore that might say what happened to William?
Best wishes Sandra