I was cleaning up my workshop the other day, and I found a piece of my history of exploring "the art of making Colloidal Silver ." It is five 1988 Canadian silver Maple leaf coins. I got these as soon as they came out to have a source of silver of which I could be sure. The 12gauge silver wire that I had them linked with is 999 from a reputable company, but with no knowledge of what the impurities are. I continued to be frustrated in my experiments to control particle size while attaining high levels of ionic content. As you can see from the picture, the silver oxide buildup on the Maple leaf coins was very heavy and required wire brushing to clean it off. The reason for the corrosion was the numerous indentations on the coins themselves. These indentations formed walls spaced so closely together that ions were not allowed to fully escape the Maple leaves without combining and forming particles of silver oxide which would then attach themselves to the surface. When I would grind the silver oxide off with a wire wheel, the scratches formed and the same phenomenon would repeat itself.
This difficulty is caused by what is called the "Nernst diffusion area." It describes the limits for how many ions can escape from a given surface area, even a completely smooth area. Having indentations such as those on the coins means that walls were formed with the distance between them less than the diffusion area.
So for those of you who are using Canadian silver Maple leaf coins, I can assure you that I agree with your reasoning completely. When it comes to what I'm going to put into my body, I'm not a "trusting" person. If I did not have a source of silver wire that I was certain of, I would still be using Maple leafs myself.