Is it possible that American Silver Eagles (or any other types of new coins) might have some sort of coating on them to keep them new looking? I have a few (I believe) un-circulated American Silver Eagles.
Acrylic spray coating works just fine, easily removed with an acetone bath later on.
Problem: the coating may? chip or peel off in tiny areas, thus only differentially protecting the coin in parts. This may? otherwise lead to blotchy protection on a coin that has been coated. That could lead to blotchy toning years later.
A hard, clear, acrylic capsule is therefore still needed to keep the coating fully intact. That's how new proof mint product is often packaged anyway, but without the coating. Local coins shops should be able to supply capsules of appropriate size. My LCS does.