There was a discussion there several months ago about whether or not blue and purple colorfully toned copper is AT or if when coincare or MS70 are applied to the surface of UNC brown copper coin the surface contaminants or brown tone is removed to reveal the colorful blue and purple toning underneath. Some of the biggest names in copper coins were arguing on both sides so I bought some MS70 thinking I would experiment. The bottle sat on my shelf for months and I finally got around to it. I don't claim to be a chemist and others might be able to explain what is happening better than I can, but it seems to me that the MS70 is not applying any color to the surface, but reacting to certain surface toning to change the color. Some of the coins had no change other than to appear brighter, while others changed color completely. A member on the other forum suggested the color change is also reversible, but the thread got pulled before any explanation was given. My main goal is to start a discussion about whether or not this type of treatment is considered market acceptable(because there are many similarly toned coins in tpg holders) and also to gain some insight into what coins are supposed to look like and how different chemicals affect the coins.