PART VI. Striking Errors:

Machine Doubling:

Rim-restricted design duplication

Definition: A rare form of doubling that almost always appears on the face struck by the hammer die. After reaching the lowest point of its downstroke, the hammer die bounces up, shifts to one side, and lands lightly on the design rim, leaving a set of raised design elements. Rim-restricted design duplication (RRDD) has been detected on 1994 (several die pairs), 2004, and 2006 cents; several Presidential dollars (Washington to Madison); and certain quarters and dimes where the peripheral letters hug a very narrow design rim. A 1979 Italian 100 lire coin displays RRDD on both faces, marking the only issue known to me in which RRDD appears on the face struck by the anvil die. RRDD can co-occur with push doubling, but this is uncommon. When the two forms co-occur, they don’t necessarily point in the same direction.

A 1994 cent featuring rim-restricted design doubling in the northwest and northeast quadrants of the obverse face.

This 2006 cent features rim-restricted design doubling in the northwest quadrant of the reverse face. After reaching the lowest point of its downstroke, the hammer (reverse) die bounced up, shifted to the northwest, and landed lightly on the newly-struck design rim. Discovery and images courtesy of Sonya Esquibel.