Ultra Scarce 1940s Glenn Colorule for Testing Color Vision dansk international Craven (there is some debate

Craven (there is some debate about it from what I've read

Because of its size I shot it in fairly crummy lighting with some shadow--the color is richer and pencil a bit bolder in person

Crazing to the glaze

which stains and etches easily

12 years old

Ultra Scarce 1940s Glenn Colorule for Testing Color Vision dansk international Craven (there is some debateI have found a bunch of academic papers and studies discussing the use of the Glenn Colorule, but can't find even a picture of another out there anywhere. There are records of in a few academic libraries, so I know it was produced by s explained on the box text, it was made to be used to test the color vision of observers, to test the quality of light sources, and or to demonstrate disagreement caused by "pseudo," or false, color matches. There's a