Some of the portraits bear a photographer's stamp or more specific date (occasionally contradicting other prints of the same photograph).
Dr. Arnold O. Beckman (1900-2004) invented the first commercially successful electric pH meter in 1934 and thus began a long career manufacturing scientific and medical instruments with National Technical Laboratories, Arnold O. Beckman, Inc., and Beckman Instruments. After his retirement he devoted his life to philanthropy and specifically supporting scientific innovation.
Rothschild Photo, Larry Harmon, Jean Raeburn, and T. A. Dietrich. “Portraits of Arnold O. Beckman (1900-2004),” 1950–1959. Beckman Historical Collection, Box 56, Folder 67. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/f4752h16g.