This post is mostly for fun since it is not a deliberate or intentional photographic print, but how it happened may interest you.
What you see is a chemical reaction between the residues in the original photograph’s emulsion (the fixer chemicals, most likely) and the acids in the back of the cardboard cabinet card mount of another photograph. If someone stacks photos on top of one another like a deck of cards, then puts them in a box or drawer where they remain undisturbed for many years, one photo can chemically “burn” its image into the paper surface of the photo on top of it. Often this image is indistinct and rather ghostly, more so than you see in this example; the image may not be particularly interesting so you pay little attention to it.
The original print (which I hope someone still has) would have been crisp and the fine details would be present, but because of the coarseness of the fibers in the cardboard mount, most of that detail has been lost, yet this ghost print still preserves a remarkable amount of tonal range. A portion of the top of the image is missing because of the way the deck was stacked (pun intended). The chemical image is the reverse of the original, so below you see the proper orientation and some enhancement. When working on such an image it is difficult to decide what is real (part of the original image) and what is not (there is guesswork involved).
By chance, when I have come across the “ghosts” I have never had the good fortune to also find the “corporeal” photos they represent.
