Here is a picture of the elusive CD 211 NO LEAK D in a medium green. Included in the picture too is its companion insert or ring. When used together on a pin, they formed the "perfect leak free seal". The CD 211 was made by BROOKFIELD and saw limited production and very remote distribution. Many of the known examples of the NO LEADK D have been found in small pockets in Washington, Oregon and California. As far as I know, they only came in Aqua, Dark Aqua, Green Aqua and in an unlisted Green. According to those that use to hunt and find them in the late 1960s and early 1970s, the rings are even tougher to find. Roomer has it that the NO LEAK D was placed on a special two pin bracket on Stamped Pass in Washington State. To date, I have not been able to prove this to be true.