This Type 2 $1 Gold brockage is unique for the type, and only 1 of 2 known in the entire $1 gold piece series from 1849 through 1889. The other known piece is a Type 3 dated 1874 and was authenticated and certified MS 62 by NGC.
All United States gold mint errors are extremely rare and valuable. This gold error came out of a Stack's auction over 30 years ago and has been in several major collections. Since the Type 2 design was only struck from 1854 through 1856, it is incredible that this rare type of mint error occurred in this series and was saved for over 150 years.