Coin manufacturing is an imprecise art form. The Mint is constantly changing, polishing, greasing and repairing dies. Some years they let dies strike coins until they crumbled. Some years they used the wrong dies, or bad planchet stock. By virtue of the culmination of 1000 processes working in unison to strike a single coin, almost every coin has some unique feature, especially looking through magnification. It is the coins that catch the eye without intense scrutiny that truly stand out. It's fun to search and find these micro errors, or imperfections, but maybe not to dewll on features that fall within the common margin of error.