1986 Mint D Lincoln Penny

Clear closeup photos would help us tremendously. From what I can see, the 8 in the date looks to be a plating blister, which will soon (if not already) expose the grey zinc core metal which will soon led to zinc rot which will eventually eat your entire coin. Lots of these show up nearly everyday. It's damage; spend it while you can and keep searching!

Your on it
John1

I wasted a couple years at other sites only to be misled. Since I have been here, I have learned a lot and people here are nice and helpful. Trust what you see at this site, there are experts to guide you in the right direction on collecting coins.

Damage is a vague term. Damage to the coin is not a mint error. Split plating is not a premium for a coin. Mostly what you are seeing is damage and split plating rot. The line behind the motto (the top letters of the obverse) are showing Ridge Ring. This is Die Deterioration. Not an error either. Just a tired aging die, that is no where reaching retirement yet.
1. Split plating zinc rot on the mintmark and the '8' on the date.
2. Ridge Ring on the motto area.
3. Stain on the coin from possible contact with soda in a cup holder.
None of these are errors. They are just what happened after the coin was struck. Just a vague term used that often new collectors use, when they are just learning. Learn what has a premium for a coin, then you will know more about what to look for on collectable coins. Study the sites that list Doubled dies, RPMs (Re-Punched-Mintmarks). These are die varieties, not errors.
https://www.coppercoins.com/
http://www.varietyvista.com/index.htm
http://www.doubleddie.com/1801.html
These will show you the listing of die varieties. Also it will show descriptions of that makes it a die variety.
Error coins are a different ball game. These are mint errors. More of One time event that involves something the mint did that happened usually just once.
Die events are not mint errors. Die events are like wrinkles on a Senior person. Events that happen during the life of the die. These are common events, and usually don't have a premium for these.
Striking events can be also one time events and have a premium. But other things like Machine Doubling and other common events won't have a premium for them. To learn more about Mint errors You can Study this site:
https://www.error-ref.com/
This is like the college of error coins. So it take a lot of patience to learn all this information. Just like school, it takes time to learn. And always remember, you will never know it all. It still is teaching me new stuff all the time. New events happen that add more information on what you didn't know about.

So learning more on a subject helps train your eyes as to what to look for and when you see something, know what you found. Even common events that have no premium is helpful. Why, because then you can move on to the next coin, know what happened to the one you had in your hand. On the top of the page of the forums, there is a section that will help with the process:

Look for this link and start with the last pages first as it will be easier to understand. (As I add to information, I get better at explaining the subjects) Always learning, and adding new stuff even daily. That is how you train your eyes.

CoopHome: What are some methods of learning how to grow in knowledge of coins? looking for information that will help you to learn more on a subject. if you were traveling, what do you do first. you check out a map to see where you are going and how to get there. but suppose you decided to for get looking at a map and decide to go it on your own. where would you end up? you would have to check a map to see how to get back home. so know where your going first. (if you really want to get to where you are going.)