The photograph of my great-grandparents was mounted on a piece of heavy paperboard. My grandmother has written on the reverse side of it–writing that is on the paperboard and not on the picture.
Today, approximately 100 years after the picture was mounted on the board, the glue gave up the ghost. The photo had been freed.
It was freed from the paperboard and potentially from being identified. How many of your identifiers are not really attached to the picture?