PART VI. Striking Errors:

Machine Doubling:

Incused Machine Doubling

Definition: Machine doubling that affects design elements that are normally incuse.

The example shown here is a 2011-D Olympic National Park quarter. Peripheral design elements on the reverse face are all incuse. In this specimen the letters E PLUR show strong machine doubling. After reaching the lowest point of its downstroke the hammer (reverse) die bounced up, shifted toward the northwest, and landed lightly on the elevated ring that encircles the reverse face. This left a lightly-impressed set of letters offset from, and overlapping, the normal incuse letters. These extra letters are much smaller and thinner than the normal letters because the apex of each raised letter on the die face is narrower than the base in vertical cross section.

Coin courtesy of Alex Tuel.