The American Numismatic Association (ANA) recommends storing coins in acid-free envelopes or “flips,” which are mylar cases that should not contain PVC, or polyvinyl chloride.

While most collectors understand this, the average person does not...    so here is a little back to the basics to help you out...

Definition: A flip is a small PVC, Mylar, or plastic pocket that folds in half, and is designed to hold one just coin (sometimes people cheat and put one on each side but then you cant see Obverse and Reverse (Front/Back) at same time. Flips usually measure 2 inches square (when folded) - THE STANDARD, but they also come in oddball 1.5 inch and 2.5 inch sizes.

Usually, the collector or dealer puts a ...