Always make an image of the back of photographs. Even if the back does not contain specific identification of the individuals, place, or event in the picture, it may help you determine what photos were taken at the same event.
I have a number of photographs that were taken at a wedding in the greater Chicago, Illinois, area in the 1950s. They were scattered throughout several boxes and folders of pictures obtained from several different relatives. The photographer’s stamp on the back at least confirmed that they were taken at a function associated with the wedding. That’s a clue to assist in identifying those people who are not personally known to me.