Hi, I wonder where we can get the case/holder for the individual PM coins. I assume you don't just put your coins in a bag or box or envelope where it is easy to get exposed to air/humidity and other contamination. I kind of like the case that's used for the W-series ASE, which is almost air tight and transparent. But I wonder where to get the appropriate case for other coins, especially the gold coins can be much smaller given their density. Thanks!
Try JP's Corner. They carry a large selection, have good quality, reasonable and are reliable. http://www.jpscorner.com/
You may also want to consider intercept shield holders. They are a little bit more expensive than the airtites but are supposed to help reduce risk of toning. I have had good luck purchasing them from Brooklyn Coin Gallery. TC