Actually, some older systems did start with A. Like chicken eggs, there were even grade AA and AAA diamonds.
In the 1920s, before the Gemological Institute of America (GIA) introduced its D-Z system, color descriptions for diamonds had been developed for purposes of sales, not science. Vague adjectives like canary yellow, white or blue-white were used. Diamond dealers were using 1, 2, 3 or I, II, III as well as A, B, C in their grading sc... more