I recently picked up a box of 2021 Shield Cents to search for new errors and varieties. While searching the first roll, I came across a pretty nice strikethrough error, which was exciting! What I did not expect to find was the progression of this strikethrough on other shield cents within the same roll and next 2 rolls. I know that there are such things as early, mid, and late die states for many doubled dies, but I did not know a similar thing existed with strikethroughs as well. Below are the examples the best I could photograph them as well as a small description of each one. (Photos should be in the order as listed) 1. Early Progression: Very minor strikethough error on the back of Lincoln's neck as well as in front of his mouth and below the beard. 2. Early-Mid Progression: Strikethough becomes more pronounced in front of Lincoln's bust as well as on the spot on the back of his neck. 3. Mid Progression: Major change with a larger strikethrough going towards the date touching the 2 and barely touching the 0. The other strikethrough areas have also grown, but not as large. 4. Mid-Late Progression: This example is very similar to the mid progression example, but on this one, the strikethrough is slightly deeper into the penny as well as moving closer to the 0 in the date. 5. Late Progression: The strikethrough is much deeper into the penny than the previous stage, and has now taken a part of the 2 and first 0 off on the date. The smaller strikethroughs around the bust is now much more pronounced than the previous stages. I also tried to get a picture of each penny entirely, but if they are slightly blurry, my apologies. Stage 1 is not there as a full example as I can't upload any more images haha. It may be difficult to tell the depth of stage 5, but it is definitely deeper than the other examples. Figured this was too cool of a phenomenon not to share! I have also never witnessed this first hand, but rather only heard about it. I am not sure if this is uncommon to have the examples of progression or not, but I still consider it really interesting!