The brochure details the components and specifications of the Model R pH meter, manufactured by National Technical Laboratories and branded as a "Beckman pH Meter."
Arnold Beckman invented his first pH meter in 1934 at the request of a chemist from the California citrus industry, who needed an accurate way to measure the acidity of his product. The resulting instrument kicked off rapid development not only of Beckman Instruments, Inc. but also of the electronic scientific instrument industry.
Beckman Instruments. “The Beckman PH Indicator for Continuous Measurement of PH with the Glass Electrode,” 1939. Beckman Historical Collection, Box 20, Folder 2. Science History Institute. Philadelphia. https://digital.sciencehistory.org/works/6w924c74z.