http://www.ebay.com/itm/Original-Chevrol...=p2047675.l2557
According to this seller these plates that I assumed were older GM produced plates were actually made by Quality Chevrolet, a GM dealer located in Wichita Kansas. Also according to the same seller the colors changed from year to year, depending on what the colors of Kansas plates were that year. Evidently the seller knows what he is talking about or he has a really good line of BS, cause he has sold a bunch of that style plate in different colors and of varying quality.