I think it's one of those early color photographs. Basically, a photographer would take three photographs, each with a different color filter. Those photographs were black-and-white, where the value corresponded to the saturation of one of the filter's colors. They were then projected onto a final image using collotype printing with a different dye for each black-and-white photograph. This process can give you all sorts of colors by mixing three primary colors of dyes, but it's tricky to make photographs align perfectly. As you can see, there are stripes of cyan, green, and red on the contour of those people, as well as some blur, and that's because it's hard to stand still between photographs, or a wind could make your clothes move a little, etc.
