Those edges are from an instant roll film camera, the first one of which was the Polaroid 95, released in Nov of 1948, so that is the earliest that photo could have been taken. In 1963, Polaroid came out with cameras that took pack film (which had smooth edges.) They still made roll film cameras and people still used them past 1963, but it may be more likely that pack film was more common as the 60s wore on, so my guess is that the photo was taken in the 1950s.
So if the guy on the right was born in 1920, he would be 28 at the youngest in this photo. He looks older, though. Maybe 10 years older, or so? I'd say late 50s.