Part VI. Striking Errors:

Collar Shimmy

Definition: Deformed or smeared reeding that is generated while a newly-struck coin is still pinned between the dies.  The abnormal reeding is caused by rapid oscillation of the collar, sometimes supplemented by horizontal movements.  The newly-struck coin may have been initially struck within the collar, or partly or completely outside the collar, with the collar “popping up” and shimmying while the coin was still fixed in position by the dies.  Collar shimmy is known among 1976 Argentina 50 centavos coins and one domestic coin.

This 1996-P quarter dollar represents the only known case of collar shimmy among domestic coins.

The planchet was slightly uncentered and was forced down into a collar that was frozen in a partially deployed position.  This created a stiff collar error (with a strongly cupped unstruck crescent) and a partial collar error.  After the hammer die reached the lowest point of its downstroke, the collar sprang up (probably in a tilted position) and was driven deeply into the coin’s edge between 6:00 and 9:30.  The collar then twisted back and forth, pushing some reeds to the side and other reeds together.

Other errors that appear on this coin include a horizontal misalignment of the hammer (obverse) die toward 6:30 and a die attrition error that extends from 9:30 to 12:30.  Stiff collar errors, die attrition errors, and horizontal die misalignments all result in collar impacts.  Such impacts could have destabilized the collar, facilitating the collar shimmy error.