Why Don't Machine Doubling Errors Get More Respect?

Wow, that 1991 cent is amazing.. Is that a variety or a unique error?

IN GOD WE TRUST is not affected on this 1991 cent because its relief is lower. The die bounced up after impact, shifted to the left, and landed on the design with a bit of a secondary bounce. The die didn't sink into the design deeply enough to affect the motto.

In case anybody's curious, my take on when the minting process ends is when a coin leaves the striking chamber for the last time. Any mishap that occurs within the striking chamber, or that affects the protruding portion of an off-center or expanded coin while the rest of the coin remains inside the striking chamber, is a mint error. The defect must be one that could not occur outside the coining press. Of course, the end of the minting process occurs later for small dollar coins with edge lettering. The lettering is applied well after the dollar has left the press. The advantage of my definition is that it incorporates such eye-catching phenomena as ejection impact doubling.

That's an impressive number of shelves. I don't recall seeing a number greater than that on domestic coins.

@MikeDiamond I like your cutoff point of the striking process ending when the coin leaves the striking chamber for the final time. Makes far more sense and captures errors like double denomination, die caps, and double strikes.