This famous error show the obverse of the 1858 flying eagle cent with small letters struck uniface on a half dime planchet. This is believed to be a piggy-back planchet which rested on top of a cent blank when this was struck. It was listed in the Adams and Woodin book as a pattern.
It is similar to another mint error P3188
which was struck in a similar manner but over a struck half dime.
The piece is unique and is ex-Scott 7/1880 lot 474, Woodside, Woodin, Brenner-1914 ANS, Brand, Ruby-Superior 2/74, NASCA 10/79, Schornstein, HIM 11/82, Cowell, Lighterman collection - NGC63
Photo courtesy of Mike Byers.