This famous Bust Half mint error was from the Logan Collection auctioned during the 2003 ANA in Baltimore. It is one of only six known plain edge Bust Half Dollars in the entire series. It appears to be broadstruck since it is on a Type 1 blank planchet.
This fascinating bust half dollar completely lacks edge lettering and as such is extremely rare, with only a handful of specimens known for the entire lettered edge bust half dollar series (1794 to 1836). These few “plain edge” piece happened because they did not receive the first step in the minting process: the feeding of the blank through the edge-lettering machine that applied the words “FIFTY CENTS OR HALF A DOLLAR” to the blank’s edge.
This lettering machine, known as a Castaing machine for its inventor, the Frenchman Jean Castaing, consisted of 2 flat bar dies, one fixed in place and the other moving. Using a hand crank, the blank was rotated between the bar dies as the lettering was pressed into the coin. The distance between the bar dies was slightly less than the diameter of the half dollar blank, with the result that the rims of the blank planchet were raised and its diameter became smaller as it rotated through the machine.
Because this coin didn’t pass through the Castaing machine when it was a blank, its diameter is slightly larger than normal. The distance from the stars to the edge on the obverse is greater than usual, and similarly the distance from the tops of the letters to the edge on the reverse is greater than usual.
In addition, the edges of this coin have a much different look. All around the obverse, the outer edge is rounded as it makes the 90 degree transition into the edge; all around the reverse, the outer edge is sharp as it makes the transition. This is because the blank was punched out of a piece of silver strip, with the result that the side of the blank that the punch pushed on had squared (sharp) edges, and the side which popped out first got the round edges. Of course these features would have been obliterated if this piece had passed through the Castaing machine.
Among the few known plain edge bust half dollars, this piece shows off its unusual features to an exceptional degree, and its high grade magnifies its desirability. It is a wonderful and rare error coin!