Image © My personal collection.
This back of an carte de visite photo, from an album of my Grandmother's. It is the back of the photo of the woman standing that I posted a little earlier.
Although the photos were know as 'carte de visite' they were not actually a visiting card for the person in the photo, but they were an inexpensive way for family and friends to exchange photos. A close look at the upper left corner shows - $1.00 Per Dozen.
Gradually, the photographer's logo became more and more prominent and gives a clue to dating these little 2 1/2" x 4" photos. The larger the logo, the closer to 1900. Free advertising for the photographers of the day!