Is This Woman a Dupont OR Granter

Does anybody recognize the woman in this tintype photograph given to me by my Aunt Winifred Granter (1919-1993) in about 1992-3. Aunt Win said she was a Dupont, but I can't remember if Win explained her connection with us Granters. By the date of the popularity of tintypes, say 1860-90, it might have been taken in Bristol or London. (The original is the reverse image, as I understand this is how tintypes were processed).
Bit of a long shot I know.
Regards, Jim Granter