Strike Through (Grease) – Also referred to as a filled die strike, this error occurs when part of the incused area of the die becomes clogged with grease, causing that area to not be struck clearly or not at all. These are the most common of the strike throughs. The grease that falls onto coins is usually full of small metal flakes causing unique markings in the filled areas. They will look off color from the rest of the polished fields.

this cent was struck through grease.