Great example of it. You really captured it in that photo. Flat and shelf-like. If it were actual hub doubling it would have the same rounded look for both impressions. This has a sharp contrast...almost like a smear.
Think about how a die was made (before the single press process). The working hub presses the working die, the working die is annealed to relieve work hardening and the process is repeated. A doubled die occurs when there is a slight misalignment during one of the pressing steps occurs. On your coin, notice how the highest impression of the D and E are thinner than a normal letter. It's not possible for the working hub to impress a thinner letter into a die, but a loose die shifting in the press as the coin is struck will certainly leave a thin letter. Also notice how the lower most impression is flat. Once again, this isn't caused by the working up, its caused by a loose die in the press. Recognizing thinner devices, flattened devices, and looking for split serifs are some keys to identifying true doubled dies Go to this tab on Wexlers site, scroll down, and click on the links for each diff class of doubling. https://www.doubleddie.com/58222.html This is the same tab that has info on the characteristics of a doubled die. I believe if you start to get comfortable with the info in this link, the puzzle pieces will start to fall into place. Also, keep reading about the die making process.
