I was browsing one of my favorite apparel sites- Mod Cloth- and happened on this adorable wall clock.
You can click on the link below for more info:
But, this clock reminded me of some interesting color blindness charts that I will be selling at the flea. They were produced by an inventive optometrist Israel Dvorine in the 1940s to test aviators and recruits during WWII.Until this time, there were similar charts made in Japan to test colorblindness but they were difficult to obtain and reproduce. If you would like to read more about Dvorine and his charts you can click here for a lengthy and technically challenging article.
In the same vein, I have some fascinating stereoscopic charts by Dvorine for testing other vision irregularities.