Newbie: Buying First Coin, Before I Encapsulate It? Help.

It's my general practice to rinse each new raw coin in acetone with that in mind. There are things which could be clinging to the coin but as yet unnoticed which could be bad in the long term. Fingerprints don't appear for a few days, for instance, and in that time acetone can remove them.

So consistent with the rules of safety required with its' use, I always rinse new coins. There may be exceptions to the rule in the case of coins with a lot of crud on them - the surface under the crud which the acetone might remove has aged at a slower rate than the exposed surfaces, and the resulting surfaces would be contrasting and obviously cleaned. But those are exceptions.

Caution: Acetone will harm plastic slabs. Even splashed droplets. Try some on scrap plastic and you'll see what it can do.

No need to wash and pat dry. Rinse in fresh acetone and let it evaporate. Using fresh acetone for the rinse is key, or else it will leave behind whatever is dissolved into the (not fresh) acetone.