In The Solar House, I included a picture of Libbey-Owens-Ford's Solarometer being demonstrated at the 1950 MIT Symposium. In that photo (p. 128 of the book) we see Lawrence Amderson, Maria Telkes, George Fred Keck, and W.J. Arner of Libbey-Owens-Ford.

"Solarometer" was Libbey-Owens-Ford's brand. In general, this type of tool is called a heliodon, and the heliodon is still produced today. (See here.)

Here's an earlier photo of the Solarometer, from 1949.

The notice on the back reads:
SOLAR METER DETERMINES SUN'S ANGLE
CHICAGO: Ralph Sherwin shows Joan Farrell how to operate the Solarometer, developed to help architects and home builders figure roof overhang for solar houses. The Solarometer makes it possible to determine the angle of the sun in any city in the world at any time of day.