Circa 1900s. A boxed set of test colors in yarn, American Optical, each with numbered labels, each with a cover, used for the determination of color blindness. These were used for required tests of Railroad Engineers and workers. The set in good condition, the box tattered. Two sets available. 10.5 x 5 inches.
Offered by Esoterica Curiosa: Dale Beeks, specialist collector, purveyor & curatorial consultant of historical surveying & scientific instruments. Item #440