Hello yontan.
I just started looking for 'errors' on the old coins I have in storage. The names for each, how often they show up, what might be the cause, etc.
The closer I look, the more errors I find. So I've set a standard for myself. If a coin catches my eye and there is a obvious error using a 10X glass, OK.
If I have to zoom in with a 600 dpi image to find something, maybe I'm looking to hard.
I don't know if coins are pressed using cold or hot material. If hot, a Die Shift might be the amount the metal shrinks between each strike?
My experience is with wood working machinery. Most of the time, the machine is accurate. Hard, soft, wet or dry wood, and the operator cause the Variety and Errors.
