Thank you. Those 107 messages didn't answer my question. However a Google search did help.
My great-grandfather had a 'metal photo' of a family picnic. The metal was passed down to a granddaughter. No description.
The photo shows five siblings and their father sometime in the 1870s, plus a variety of children and some of the spouses.
I feel certain the photo was taken in Cincinatti, residence of my great-grandfather. The obviously pregnant woman was my great-grandmother and the four children were theirs - Spring 1878.
Imagine my surprise when another cousin (different branch) said the photo was 1873 and the children were another brother's, also in photo, the pregnant woman was an unmarried niece, which made the other lady HER grandfather's first wife, of which no photo exists. That would mean it was taken in Penn.
I was hoping the fact that my great-grandfather HAD the metal plate meant he had arranged to have the photo taken.