Now that microscopes are inexpensive, there are a lot of people finding imperfections that have always been on coins.

Although asking questions is always the best way to learn!
Your time will be a lot better spent/profitable with the following plan of attack:
If you want to catch a rainbow trout, you need to know what a rainbow trout is.
The same with coins.
Most odd looking things on coins are just post mint damage (
PMD)
Save Yourself time, effort, and disappointment...don't learn the coin hobby backwards. 
Looking for random anomalies on coins and hoping they match up to something collectable will take you a lot more time, wasted effort, and disappointment repeatedly finding out you have nothing but post mint damage or useless
Machine Doubling,
Die Deterioration, etc.
Spend some initial time at places like error-ref.com, doubleddie.com, varietyvista.com, conecaonline.org, coppercoins.com etc. to find what actual and collectable coin errors look like.
A good way to start is, for instance, separate a bunch of pennies by date. Go to varietyvista.com and, date by date, use the reference there to see what errors are known for that specific coin/mint mark. Look for those specific errors/varieties using the pictures provided. After doing this for awhile you will KNOW what an actual error looks like and not have to waste time on face value and damaged coins.
