This image shows a common illusion, created by the limited field of view provided by the photo, which tricks the eye into thinking the background is correct and stable while the foreground is changing.
There is no description on the back of this card.
This is not the best composed picture to create the illusion, as the board the two men are standing on is clearly visible and indicates some of the reason for the visual effect. However, the left side subject does appear smaller in both photos, even though the person there is exchanged.
This photo likely dates from the 1940s.