As shown in the previous two images, this John Adams Proof Presidential Dollar, found by Mendy Copley, was struck off-center on both sides, but not uniformly so, indicating a possible misaligned die error. However, when the coin was examined by NGC, they found it to have a "horizontal planchet error," which is explained on the previous two pages. But this isn't the end of this mind-boggling coin's error! It also has a very high so-called "wire rim!"
As shown in the photo, the highest point of the "wire rim" is on the left side of the image. It then traces around the top of the image and down the other side of the coin. Error coins expert (and CONECA president) Mike Diamond tells us that the proper term for this type of raised-extra-metal-around-the-rim error is a finned rim. The cause of this error is usually one of two things. Either the planchet is too heavy for the normal die spacing, or the dies are improperly spaced and coming too close together during the strike. This causes excess metal to squeeze up between the dies, resulting in the extra bit of raised metal around the rim. At first glance, it would seem likely that the latter problem is what accounts for the finned rim error here, since the dies seem to be misaligned, but in reality the planchet was cut into an elliptical shape!
As shown in the photo, the highest point of the "wire rim" is on the left side of the image. It then traces around the top of the image and down the other side of the coin. Error coins expert (and CONECA president) Mike Diamond tells us that the proper term for this type of raised-extra-metal-around-the-rim error is a finned rim. The cause of this error is usually one of two things. Either the planchet is too heavy for the normal die spacing, or the dies are improperly spaced and coming too close together during the strike. This causes excess metal to squeeze up between the dies, resulting in the extra bit of raised metal around the rim. At first glance, it would seem likely that the latter problem is what accounts for the finned rim error here, since the dies seem to be misaligned, but in reality the planchet was cut into an elliptical shape!