I dont know if you can tell by the pics, I was taking pictures for about a half hour on this one coin to try and get the whole crack. But the crack comes from the rim of the penny and splits at Lincoln's hair line and goes to the right and stops on his hair line right past the E in We, and the crack splits to the left and goes downward about halfway to his ear. . Does that make it a shatter? Or just a crack? Also the coin is in really good condition. But it is 2019. Does this add any value? If not, it's still really cool. It was hard to notice
No real added value. Not common but not rare. Better known as a spiked head. http://cuds-on-coins.com/spike-head/
The Doubled Die varieties that are considered major are really almost impossible to find. Rare errors are a different category. This might help. It provides a list... https://www.ngccoin.com/news/article/1655/Variety-versus-Mint-Error/ And https://www.pcgs.com/news/mint-error-or-die-variety
Here is good information on Doubled die coins if you haven't seen it https://www.doubleddie.com/58222.html
Cherrypickers is good resource IMO. But there are a number of legit websites that cater to what I consider the "curious" error/variety.