"Ramsay Garden's Silhoutypes", wall chart printed on one side with test types for assessing visual acuity of children or illiterates, made by Clement Clarke Ltd., London, 1920-1940 "Ramsay Garden's Silhoutypes" wall chart 1920-1940
Book of Cowell test-types for assessing visual acuity, George Cowell, inventor (type), English, 1880-1920 Book of Cowell test-types for assessing visual acuity 1880-1920
